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Scientist comment on the extreme heat warnings issued by the Met Office for the week beginning 22nd June 2026
Prof Xueyu Geng PhD, FICE, FGS, FHEA, CEng, Professor in Geotechnical Engineering, Built Environment and Sustainability Cluster Lead, University of Warwick, said:
How do buildings and transport networks cope with heat?
“When temperatures rise this sharply, and for this long, the effects ripple across everything we have built, our homes, our offices, our railways, our roads, the very ground beneath them. Buildings struggle to expel heat they were designed to retain, and cooling systems are pushed beyond their capacity. And beneath the surface, in the soils and earthworks that carry our transport networks, changes are happening that are invisible to the naked eye but deeply significant to those of us who study them.
“The rails that expand and buckle in the sun. The road surfaces that soften under tyre loads. And perhaps most critically, the earthwork embankments and slopes that have carried our trains and traffic for generations, and whose stability depends on a delicate balance of soil moisture, root systems and ground pressure that prolonged heat quietly but significantly disrupts.
Railway track buckling:
“Steel rail expands significantly in extreme heat: a 1°C rise in temperature causes roughly 11mm of expansion per kilometre of track. Rail is installed with a ‘stress-free’ temperature in mind, and when ambient and solar-radiation temperatures exceed that threshold, the track can buckle laterally, what the industry calls a ‘sun kink’. This is why speed restrictions are imposed on the network during heatwaves; it is not a precaution, it is a structural necessity.
Road surface degradation:
“Sustained high temperatures soften bituminous asphalt surfaces, leading to rutting, shoving, and, very visibly, tyre-contact marks at junctions and bus stops where vehicles sit under braking load. These are not cosmetic issues; deformed surfaces affect drainage, vehicle handling, and the long-term structural integrity of the carriageway.
Embankment stability:
“Perhaps the least visible but equally serious risk relates to the earthwork embankments, the engineered soil structures that carry railways and roads across the UK’s landscape. In normal UK conditions, vegetated embankment slopes benefit from what geotechnical engineers call ‘unsaturated soil suction’, a negative pore water pressure that gives soil additional strength beyond its basic material properties. Plant root systems reinforce this further, binding the soil and drawing moisture through transpiration. Prolonged extreme heat disrupts both. As soil desiccates, it shrinks and surface cracking develops. Vegetation under heat stress dies back and loses its root tension. The embankment becomes, in engineering terms, progressively weaker, quietly, and without any visible warning sign at the surface. The critical moment comes when intense rainfall follows: severely desiccated, cracked soil does not absorb water efficiently. Water runs off the hardened surface, dramatically increasing erosion, while water entering the crack network can reach depth rapidly, creating sudden and significant changes in the stress state of the embankment, exactly the conditions that precede slope instability.
Are there any specifics related to this forecast heatwave that present engineering challenges?
“This week’s heatwave brings all of these risks into sharp focus simultaneously. The Met Office has forecast peak temperatures of 38°C in southern England, potentially breaking the UK’s June record, with overnight temperatures remaining above 20°C, what forecasters call ‘tropical nights’. Perhaps most striking is the humidity: dew points forecast at around 22°C this week, compared to single figures during the record-breaking 2022 heatwave. And critically, this is not a single hot day, it is a sustained, multi-day event, with thunderstorms and intense rainfall forecast to follow as the heat breaks down.
“From a ground engineering perspective, every one of these factors matters, and they matter not just for managing today’s emergency, but across the entire lifecycle of infrastructure, from initial design through to long-term maintenance. Temperature, humidity, duration, and the pattern of heat followed by intense rainfall are not just weather statistics; they are the conditions that determine how soils behave, how slopes perform, and how earthworks age. What makes this moment particularly important is that we now have decades of climate data that allow us to understand these patterns and, increasingly, to predict what is coming. The challenge is knowing what to do with that knowledge, especially for infrastructure that was built long before we understood what today’s climate would look like. Modifying or retrofitting existing earthworks, embankments and transport structures is far more complex and constrained than designing new ones from scratch. Existing assets have fixed geometries, live operational pressures, and physical limitations that make adaptation genuinely difficult. Yet that is precisely the challenge we must face, because the infrastructure that Britain built first, and that has served us longest, is also the infrastructure most exposed to a climate it was never designed for.”
John Lawrence, Chair of the IET (Institution of Engineering and Technology) Railway Technical Network, said:
“Heat is a significant issue for the railway, affecting both infrastructure and trains.
“Managing it is a cross-industry exercise running all year round, built into the seasonal preparation carried out by maintenance teams and planners across the network. The areas hit hardest by heat also tend to cause the most disruption.
“Ambient temperature and solar gain combine to push temperatures very high at track level and in trackside equipment. Track buckles and dewirements are what really worry engineers – despite years of focus, investment and improvement, rails can still buckle in extreme heat.
“That brings derailment risks, and overhead lines can sag and catch on pantographs, halting train movements or forcing lengthy reroutes.
“There are hidden failures too. Signalling control, power supplies and trackside telecoms can all suffer heat stress, and rail expansion can cause switch-creep that stops trains being routed through points safely, so a signalling failure a passenger sees may actually trace back to overtemperature elsewhere on the network. Lineside fires, sparked by anything from discarded rubbish to passing trains, can cause further disruption.
“These issues are costly and time-consuming to manage, and they’re becoming more frequent as high temperatures increase. You might notice rails painted white to reflect solar gain at known risk points, upgraded tensioning equipment on overhead line gantries, fresh ballast to keep rails in place, and lubricated joints to allow for expansion.
“What passengers don’t see is the hidden technology tracking conditions and flagging early warning signs – weather forecasting across short, medium and long timeframes to help planners react; rail stressing to maintain consistent tension; vision systems checking pantograph contact; yellow trains monitoring track stability; temperature sensors on the rails; and points and signalling systems checked for defects.
“It might also surprise people that thermal imaging drones and helicopters are used to spot overheating equipment, with inspections and repairs often carried out overnight.
“Temperature management is a major issue for the railway and a constant focus of research and development. With the climate changing, it’s an issue we now have to manage every day.
“One of the simplest ways we tackle overheating tracks is by painting them white, which can lower track temperature by 5°C and cut the signalling failures that cause major disruption. It’s a technique used elsewhere too, in countries more used to high temperatures – in Italy, for instance, engineers often paint the inside faces of rails white to reflect sunlight and reduce the risk of buckling.”
Prof Lucelia Rodrigues, Head of Department of Architecture & Built Environment, Professor of Sustainable and Resilient Cities, University of Nottingham, said:
“The biggest threat from current and future heatwaves may not be outside since in the UK we spend 90% of our time indoors. Better design, not more technology, is the key to protecting health in a warming climate.
“The solution to make buildings comfortable is not expensive or energy-intensive technologies – it is better design. Climate change is increasing the frequency, duration and intensity of heatwaves in the UK, making overheating in buildings a critical challenge for the future.
“Many UK homes were designed to retain heat during winter and can become dangerously hot during prolonged periods of warm weather. Yet creating homes that remain comfortable throughout the year does not have to cost more. By designing buildings that respond intelligently to the climate – making the most of winter sunshine, providing effective summer shading, encouraging natural ventilation and reducing unwanted heat gain – homes can maintain comfortable temperatures with minimal energy use. When a home works with the climate rather than against it, low-energy technologies can efficiently provide any additional heating or cooling required, creating healthier, more resilient places to live.”
Dr Antonios Kanellopoulos, Reader (Associate Professor) in Innovative Construction Materials, and Director of the Centre for Engineering Research, University of Hertfordshire, said:
“Most domestic buildings in the UK are optimised for keeping heat in and not out, which practically means use of heavy insulation, well-sealed building envelopes and minimal external shading. In a heatwave, houses can turn into an oven, affecting the comfort levels of inhabitants. Short-term solutions to improve comfort can include: use of curtains to block south or west facing windows (such windows in direct sunlight can emit ~700 Watts per square meter; almost like a small electric heater), use of external shading if possible (e.g. large patio umbrellas) and ventilate through wide open windows during the cooler parts of the day (evenings and early mornings). Looking into the future and since these phenomena are becoming more often, the solutions should be more drastic involving adoption of the “passive house” principles.
“In the civil infrastructure things are slightly more complex under extreme heat conditions. In the railway network, rail-tracks are installed under tension at a specific “stress-free temperature” (typically this is around 27oC in the UK) so the track sits in compression when it gets hotter. Rail temperatures can be 20oC above air temperature in direct sun, and at that point compression can cause lateral buckling (i.e., a sideways bending and twisting) the so-called heat kinks. That is the reason why Network Rail imposes speed restrictions in heatwaves, and why some rails are painted white: reflective paint can shave 5 to 10oC off rail temperature. Roads have a similar problem. Asphalt softens and ruts under heavy vehicles; concrete slabs can buckle upwards at expansion joints. Airport runways have the same problem at scale, which is what happened at Luton in 2022.
“Bridges are generally designed with expansion joints and bearings to absorb thermal movement, so they usually cope well under extreme weather. Overhead electrical lines, both railway catenary and grid transmission, can sag when hot, reducing clearances and current-carrying capacity exactly when demand spikes during the day.
“The engineering issue underneath all of this is that design codes are calibrated against historical climate data, and the historic temperature distributions have shifted. Updating standards (for rail neutral temperatures, building cooling loads, drainage for heavier rainfall etc.) is now active work for engineers and standardisation bodies. Retrofitting is harder and more expensive than designing in heat resilience from the start, which is why this is increasingly a planning and procurement question, not purely an engineering one.”
Dr Julie Godefroy, Head of Net Zero, CIBSE (Chartered Institution of Building Services Engineers), said:
How do buildings cope with heat?
“A large part of the stock (houses, flats, apartments, bedsits, maisonettes) is not prepared, as it was not designed and build to cope with such high temperatures for such long periods of time. For example, the large majority of the housing stock does not have external shading devices, so solar gains can be high and create overheating risk even outside of heatwaves. Urbanisation compounds the issue, with temperatures remaining high at night in city centres.
“In short, solutions include: high priority: reduce solar gains, and get rid of the heat through ventilation (open windows). Other measures, such as reducing gains from electrical appliances, cooking, hot water tanks etc also help but to a smaller effect. As a last resort, you may need to install cooling.
“Solutions in the short term include: use external shading if you have it, if not consider installing temporary shade (e.g. fixing a sheet outside the windows) – if not, at least use internal blinds / curtains. Open the windows when it is relatively cool (e.g. mornings, nights if the window can be left open safely and securely), close it when it is hot outside – in that situation, internal fans (ceiling, ideally) can help with comfort); reduce other internal gains e.g. do not let electric things on that don’t need it (e.g. plasma screens). If your home is on more than 2 levels, open windows at the bottom and top levels, ideally on opposite sides; if it is on one level, if available open windows at opposite sides or if not, as a corner: this will help drive air through and out.
“In the medium term, prepare your home for the next heatwave, i.e. consider installing permanent shading, and windows that can be left open safely at night (e.g. with grilles, or high level windows with a small opening), and take measures that will also reduce energy use e.g. insulating your water tank. Consider installing ceiling fans, if your ceilings are high enough (typically more than 2.8m). Also look around your home, as hot external surfaces nearby can increase the risk inside (e.g. painting with light reflecting materials can help), while vegetation or other ways to provide shade will help.
“More detailed guidance: CIBSE TM591 provides an assessment methodology to assess overheating risk through modelling, targeted at designers and modellers. The Good Homes Alliance provides a free simple tool on assessing and reducing risk in existing homes, targeted at non-specialists like homeowners.”
Prof Hayley Fowler FRS FRMetS, Professor of Climate Change Impacts, and Royal Society Faraday Discovery Fellow, Director of Centre for Climate and Environmental Resilience, Newcastle University, said:
“The evolving heatwave in the southern to central UK is forecast to produce unprecedented temperatures for June and is predicted to break the June temperature record set 50 years ago during the record summer of 1976. Heatwaves are becoming more frequent, longer and hotter with climate change, as a direct result of the fossil fuels we are releasing as a society. This particular heatwave has almost exactly the same atmospheric circulation set up as in July 2022 which produced record-shattering temperatures over 40 degrees in the UK. The same sort of temperatures are forecast during this event, in June. We can expect to have to cope with more and more of these types of events in the years to come. Our current climate is the least extreme we will live in in our lifetimes, and certainly until we reach Net Zero, and we need to adapt urgently to live and work in these extreme temperatures.”
Dr Jess Neumann, Associate Professor of Hydrology, University of Reading, said:
“Just a few months ago we were talking about one of the wettest winters on record, yet following an unseasonably dry spring and now a second, potentially record-breaking heatwave, concerns are being raised around a potential risk of drought this summer.
“Hot weather is pushing our demand for water well beyond what is normally expected in June. Keeping cool and hydrated, taking more showers, filling paddling pools, and watering gardens all add pressure to our water resources.
“The effects of extreme heat and low rainfall on rivers, wildlife and our environment are already in motion. Many rivers and some reservoirs across the south have notably low flows, increasing pressure on aquatic life and raising concentrations of water pollutants harmful to wildlife and human health. A prolonged lack of rainfall coupled with extreme heat further impacts agriculture and food production potentially driving up costs later this summer.
“It is never too late to be mindful of our water use. Hot weather increases demands on water resources. Small actions such as turning off taps, collecting rainwater (when it comes) for use on plants, using a watering can and taking fewer, shorter showers can all help reduce our individual water footprints.
“In previous years water companies have been accused of “sleeping at the wheel” with regard to water management. Remaining attentive to the current water situation is vital if we are to ensure a safe and ready supply of water for society and the environment.”
Dr Laurence Wainwright, Senior Departmental Lecturer – School of Geography and the Environment, and Senior Researcher – Department of Psychiatry, University of Oxford, said:
“The health implications of heatwaves can be significant – especially for certain vulnerable groups including outdoor workers, young children, elderly, those taking certain medications, and those with a mental health condition.
“Humans are capable of living in a wide range of climatic extremes, from -30c right up to 50c. But our bodies need time to adjust. We are designed to cope with what we are used to, just as the infrastructure of the UK is designed primarily around cool weather rather than heat. While we can acclimatize, it takes time – many weeks in fact. When a 35c day – historically very rare in this country – suddenly appears, this is a shock to the system. Our bodies – especially our brain and heart – struggle, simply because they are not used to it and have to devote most of their energy and effort to stay cool. As such, other body capabilities (especially cognitive function), suffer. Given enough time, the body is smart enough to be able to make physical adaptations to cope with the heat. But it takes time. In very hot climates, the body adapts by doing things like increasing the plasma volume and sweat rates, while lowering the salt concentration of sweat. This allows the cardiovascular system to handle heat stress with less strain. Because UK heatwaves are usually brief and intermittent, the population rarely has time to acclimatize to it physically.
“But even when the body eventually adjusts to the heat, this is not enough in the UK to cope effectively. The country is simply not built or designed to deal with hot days – everything from our NHS and homes and offices to our shopping malls and train lines – is not meant for temperatures above 30c; mainly because these days were so rare in the past.
“The 16% of the UK population with a mental health condition are significantly affected by heatwaves. Existing symptoms can worsen, new symptoms can emerge, medication side effects can be exacerbated, suicide rates go up, and hospital admissions for mental health reasons increase by 10%.
“Sleep is greatly impacted during heatwaves. When we have ‘tropical nights’ as we will this week – where overnight temperatures don’t fall below 20c (which in a UK home could mean an indoor temperature as high as 28c), a good night’s sleep is all but impossible for most. The implications of this are significant. Less sleep and broken sleep are associated with a drop in work performance and productivity, an increase in accidents, lower school test scores (a 15% drop in a room of students with a temperature of 18c vs 28c), a decline in mental health, worsened cognitive function, and an increase in impulsive behaviours.”
Prof John Marsham, Professor of Atmospheric Science, University of Leeds, said:
“An amber alert has been issued as a high pressure system and air from continental Europe is expected to bring persistent hot and humid conditions to the southern UK, with temperatures peaking through Wednesday and Thursday. This heatwave is coming straight after a new record UK maximum temperature for May was set barely a month ago, and we may now see a new record temperature for June. We should all take appropriate action, including checking on those most vulnerable. Such heat extremes are of course made far more likely by climate change – even 45 degrees Celsius may now be possible in a UK summer. Beyond this event, it’s increasingly vital that people understand the global picture, as extreme weather across the world affects the UK, for example by pushing up UK food prices, which together with the cost of fossil fuels is driving the ongoing cost of living crisis. This will get worse and worse until we have phased out fossil fuels to reach net-zero. The good news is net-zero is now the cheapest option for the UK, now costing less than just one fossil fuel crisis, let alone two.”
Ruth Shilston MBE FIMechE, IMechE Trustee and Global Discipline Lead – Mott MacDonald, said:
“The UK is experiencing more frequent and intense heatwaves which can reduce productivity, disrupt infrastructure and even lead to shutdowns. Managing comfort in the UK’s existing building stock is challenging; it was largely designed for winter conditions, leaving many prone to overheating during prolonged hot spells.
“The engineering response considers our cities as a system. This includes reducing the ‘urban heat island’ effect through increased green spaces and planting of trees, with networks of cool spaces providing support to residents and visitors alike. Adaptation at a building level is focused on low-carbon solutions such as natural ventilation, shading and reflective materials. Other solutions involve designing buildings and infrastructure to better manage heat without relying heavily on energy‑intensive air conditioning.
“The greatest challenge is not just single peak temperatures but prolonged heatwaves and warm nights, which prevent systems and building fabric from cooling. This creates cumulative strain on assets, buildings and services – as well as on the people using those assets, buildings and services.
“To respond, the UK needs sustained investment in infrastructure and public spaces so that out buildings, transport systems and cities are designed to cope with future heat.”
Dr Chengzhi Peng, Senior Lecturer in Architectural Science, University of Sheffield; and Principal Investigator of a NIHR-funded study on heat-resilient paediatric care, said:
“This week’s forecast temperatures near 38°C, oppressive humidity and nights that won’t fall below 20°C in our cities, is exactly the kind of event that puts hospital buildings under strain, and children’s hospitals are among the most exposed.
“Children are not simply small adults when it comes to heat. Their bodies regulate temperature less efficiently, and the youngest and sickest patients, including babies in neonatal units, children in intensive care, have the least capacity to cope. Many hospital wards were never designed for sustained heat like this. They hold onto warmth overnight, so the building never gets a chance to cool down, and the spaces that overheat first are too often the ones caring for the most vulnerable patients.
“In the immediate term, the single most useful thing is knowing which wards and rooms overheat, and how fast, so staff can protect patients there first, such as moving vulnerable children to cooler areas, prioritising hydration, and using shading and overnight ventilation where it’s safe to do so. The harder, longer-term task is adapting the buildings themselves, through better shading, insulation and passive/active cooling, so they remain safe during and days after heatwaves. Our work with Sheffield Children’s Hospital and partners across the country is mapping precisely where these risks sit, and what most effectively reduces them.”
Prof Mujib Rahman, Professor in Civil Engineering in the School of Engineering and Innovation at Aston University, said:
“With the Met Office issuing a red heat warning this week, the extreme temperatures are a reminder that climate change is placing increasing pressure on our aged road network.
“Around 90% of UK roads are surfaced with asphalt, and globally there are over 40 million kilometres of paved roads, the majority of which are asphalt. While air temperatures may reach 35°C this week, road surfaces exposed to direct sunshine can exceed 60°C. At these temperatures, roads can soften, leading to wheel-track depressions (rutting), surface deformation and, in some cases, the road surface becomes shiny and slippery (bleeding).
“Repeated cycles of extreme heat followed by cooler and wetter weather accelerates pavement damage and significantly increases pothole formation, increasing maintenance costs and disruption for road users.
“At Aston University, our researchers are developing more durable road repair materials, thermally efficient road surfaces, and low-carbon, climate-resilient pavement technologies to help road infrastructure better withstand the challenges of a warming climate while reducing environmental impact.”
Dr Mireia Ginesta, Research Associate in Climate Damages Analysis at the Oxford Smith School of Enterprise and the Environment, University of Oxford, said:
“This heatwave is exceptionally intense for June. Temperatures could reach 37–38°C across parts of southern England this week, with a strong possibility that June temperature records will be broken. The current June record is 35.6°C, set in Southampton in 1976.
“The weather pattern driving this event is not unusual in itself. A persistent area of high pressure over Europe is causing air to sink and warm as it descends. At the same time, the high pressure suppresses cloud formation, allowing strong sunshine to heat the ground and push temperatures even higher.
“What is unusual is the intensity of the heat. Climate change does not create the high-pressure system, but it raises the background temperature on which weather systems operate. In a cooler climate, this heatwave would have been less intense. Human-induced warming is making extreme heat events hotter, more frequent, and more likely to break records.
“Heatwaves like this can have serious consequences. They increase the risk of heat-related illness and death, particularly among vulnerable groups. They can also lead to significant stress on agriculture, especially when extreme heat occurs earlier than expected in the season, and can disrupt transport, energy, and other critical infrastructure.”
Anna Harrison, applied Quaternary scientist, BGS, said:
“Many soils contain clay minerals that absorb water and swell when they get wet, or lose water and shrink as they dry out. Extended periods of dry weather and high temperatures are a major factor in the emergence of shrink–swell subsidence. Looking ahead, these increases in hotter, drier summers and warmer, wetter winters are projected to continue. Shrink–swell ground movement is one of the most damaging natural hazards in the UK today and presents a significant and growing economic cost. Using Representative Concentration Pathways (RCP) climate projection data, we can see that this has the potential to affect millions of British properties in the coming decades.”
Jo Parker MBE C Eng. FICE FIWater FCIWEM, Director of Watershed Associates, said:
“The forecast heatwave will see water companies working flat out to maintain supplies. In hot water people fill paddling pools, water the garden and take more showers which pushes demand up to maximum levels. Whilst stocks of raw water are good, the demand can put a lot of stress on the distribution networks, requiring pumps to work at maximum capacity and with pipes reaching their full carrying capacity. The networks are usually designed to cope with this. However, the hot weather can lead to problems with the water companies’ extensive network as it leads to a weakening of road surfaces and movement of the underlying ground which in turn can lead to more failures in the pipe networks. All the repair teams will be working flat out during the hot weather so bear a thought for them. However hot it is they must continue to wear the required protective clothing to meet health and safety requirements and although much of the work is mechanised, some hand digging may required making it hot work.”
Prof Guy Gratton, Professor of Aircraft Test and Evaluation, Cranfield University, said:
“Aviation obviously operates completely in the atmosphere and is thus affected by the condition of air, including air temperatures.
“Before flight, a major challenge can be getting a sun-soaked airliner cabin cool before flight. The air conditioning systems built into airliners are usually able to keep the cabin cool, but may need help to get it cool before flight. This can be done by connecting the aeroplane to an external air conditioning unit, or by running the aircraft’s APU or Auxilliary Power Unit: a small (and rather noisy) jet engine located in the tail to run the onboard air conditioning at full power before flight. This can all be done, although particularly in a usually relatively cool country like Britain there may not be enough external air conditioning units to go around. The result of all of this tends to be more noise and pollution, which is clearly regrettable.
“During take-off and landing, the hotter air has lower density, and that means an aeroplane has to achieve higher groundspeed before it can take-off, or conversely it can have to be at a higher groundspeed during the final approach and landing. A consequence of this is either that the take-off and landing distances tend to be longer, or from shorter runways the aeroplane can become payload limited, sometimes requiring the airlines to reduce the number of passengers on board.
“That also tends to create flatter climb-outs after take-off, which is regrettable for people living or working around any airport, as this will increase the noise footprint underneath the airliner climb-out path. Higher temperatures therefore increase noise around airports.”
Dr Heather Massey, Associate Professor in Extreme Environments and Physiology, Extreme Environments Laboratory (EEL), University of Portsmouth, said:
How do human bodies cope with heat?
“The human body copes with heat through a process called thermoregulation, which maintains a stable deep body temperature at around 36.5 to 37 °C. When deep body temperature raises above this blood vessels near the skin widen (vasodilate) to increase heat loss and we sweat, the sweat evaporates from the skin and removes heat. In addition, people naturally adjust their behaviour by seeking shade, reducing activity, and drinking fluids. However, these mechanisms become less effective when temperatures are very high or when humidity is elevated, which can prevent sweat from evaporating and increase the risk of heat-related illness.
Are there any specifics related to this forecast heatwave?
“This forecast heatwave is expected to involve several consecutive days of unusually high temperatures, typically exceeding 30 °C in some areas, which is significantly above average for the UK. A key feature of the event is likely to be elevated night-time temperatures, sometimes remaining above 20 °C, which can prevent the body from cooling down and recovering. Humidity may also play an important role, as higher moisture levels in the air reduce the effectiveness of sweating that would cool the body.
“People can stay cooler during hot weather by limiting exposure to the hottest parts of the day, typically between late morning and early evening, and by seeking shade or air-conditioned environments whenever possible. Keeping indoor spaces cool by closing curtains or blinds during the day and opening windows at night can help reduce heat buildup. Wearing loose, light-coloured clothing made from breathable fabrics such as cotton can improve heat loss. Taking cool showers or baths, using damp cloths on the skin, spraying the body with water and staying in front of a fan or placing the hands and or feet in a basin of cold water can also help lower body temperature. It is important to drink fluids regularly throughout the day, even if not feeling thirsty, to replace water lost through sweating.
Are there certain people who are more vulnerable to heat than others?
“Certain groups of people are more vulnerable to heat due to physiological, medical, or environmental factors. Older adults and young children are at greater risk because they may be reliant on others to adjust their environment, keep them cool and hydrated. Individuals with pre-existing health conditions, such as cardiovascular disease or conditions that limit blood flow to the surface of the skin or sweat loss, are also more susceptible to heat stress, as are those taking medications that affect hydration or sweating. In addition, people who are exposed to heat for longer periods, such as outdoor workers, athletes, or those living in poorly ventilated housing, face a higher risk.
Anni Feng, built environment expert and Co-Chair of the IET’s Digital Futures Policy Centre, said:
“When it’s really hot outside, many of us feel uncomfortable indoors too. That’s not just because of the building itself, but also because of what’s around it.
“Think of it like this: buildings don’t stand alone. The materials used in roads and nearby buildings can trap heat, making the whole area hotter. This extra heat can make people try to cool things down with fans or turn up air conditioning units.
“But if too many people do that at once, the local energy system might struggle to keep up. That can lead to problems like cooling systems not working properly, which could even affect things like computers and other equipment inside buildings.
“Achieving climate resilience in the built environment requires holistic, systems thinking. It demands a broad approach to understand how buildings, people and the wider environment interact, and to design for future climate conditions while working towards integrated, long-term solutions.
“When considering how we adapt for hotter temperatures, we should ask the questions like what this might mean for surrounding buildings, the environment and people in the communities – both short term and long term – and are they contributing positively to the future we aspire to create.”
Prof Lizzie Kendon, Professor of Climate Science at the University of Bristol and Head of Climate Projections at the UK Met Office, said:
“This week temperatures are going to smash the all-time UK temperature record for June. We expect increasing temperatures and the breaking of temperature records due to climate change, and indeed we are already seeing this in the observational record for the UK. What is so extraordinary, however, is the margin by which the record will be broken.”
Prof Barbara Rossi, Associate Professor of Engineering Science, University of Oxford, said:
“Before reaching for air conditioning, we should start with the measures that keep heat out in the first place such as external shading to stop direct sun hitting the windows, especially on south-facing facades and patio areas.
“There are affordable solutions online that can be placed (even just fabric) on e.g. roof windows and on skylights quite easily. Electric motorised awnings, or even outdoor shade sail, especially on south-facing facades and patio areas that can reduce the temperature inside the house by several degrees thanks to shade projection through windows. Good use of cross-ventilation in the cooler morning hours can make a huge difference for very little cost if one does it intelligently (cross-ventilation in the morning then closing south facing windows afterwards).
“Once those passive measures are in place, if cooling is still needed, I would like to underline that the priority should be given to highly efficient cooling unit that is built to last and uses as little electricity as possible.
“That is the sensible, low-carbon solution: reduce heat gain first, then cool efficiently only where necessary for as little time as possible.
“UK cannot afford cooling units running around the clock for two weeks a year, because that can add a great deal of greenhouse gas to the atmosphere, especially if the electricity mix is still not fully green.”
Prof Friederike Otto, Professor of Climate Science, Imperial College London said:
“Our first 40°C day was supposed to be a wake-up call, but clearly someone hit snooze. Hitting 40°C again – and in June this time – would be incredibly alarming.
“There’s a sad inevitability to all of this, with scientists like me trotting out the same quotes year after year. Yes it’s climate change, yes it’s us, no it’s not El Niño. Simply put, we remain on a one-way trip towards a more dangerous future, and it’s time we hit the brakes.
“Right now, children are struggling to finish their exams in sweltering classrooms and the elderly are enduring dangerously hot homes and care facilities with little relief. This heat is not an inconvenience, it is a growing public health threat. Every heatwave puts lives at risk, and it’s long past time we treated it with the urgency it demands.”
Prof Dann Mitchell, Professor of Climate Science, University of Bristol, said:
“We often see hundreds of death during a heatwave, from drownings on the day, to heart, respiratory, and neurological problems shortly after, to longer term renal and mental health problems in the weeks that follow. Everyone responds to heat in different ways, with vulnerable groups such as the elderly, babies, and people with certain health conditions being particularly affected. Anything that changes the way our body’s thermoregulation works can be problematic in a heatwave. That could be the type of medication people are on, the way they sweat, the housing they sleep in, or how their brain tells them they are thirsty.
“Having just led the UK Climate Change Risks Assessment report on health, this illustrates why we concluded that heat was the biggest risk to health from climate change in the UK.”
Dr Linda Speight, Lecturer in Physical Geography, University of Oxford, said:
“Back in 2022 when temperatures were forecasted to reach 40 °C for the first time and the Met Office issued its first ever Red Heat Warning many people underestimated the risks, with some media coverage dismissing concerns and encouraging people to head to the beach. The next day, people were shocked as roads melted, wildfires raged close to urban areas, and the heatwave led to nearly 3000 excess deaths in England.
“This time it’s not just the heat that’s a concern. High humidity levels will make conditions feel even more oppressive for everyone. We must take the warnings and advice of experts seriously. Temperatures like the ones forecast this week are dangerous and are going to be an increasingly frequent feature of UK summers from now on. Taking sensible precautions and changing plans for the week now, will save lives by Thursday.
“The definition of a heatwave varies based on where you are in the UK, as people in the south are considered to be more accustomed to consecutive days of hot weather than those further north. The forecast for this week is 10 °C degrees above the heatwave threshold in many areas, highlighting the severity of potential impacts and the need to take the warnings seriously.”
Prof Bill McGuire, Professor Emeritus of Geophysical & Climate Hazards, UCL, said:
“The UK temperature broke the 40C barrier in July 2022, so it should come as no surprise that – after another four years of global heating – here we are again. In the current climate, UK summer temperatures of 43C+ are possible, as are heatwaves lasting for multiple days with temperatures at or close to 40C. This has massive implications for health, energy infrastructure, and transport, which are simply not built for these conditions. As 40+ temperatures become ever more common, expect many thousands sleeping in the streets as poorly insulated homes become uninhabitable heattraps, widespread power cuts as power cables sag and break, transport chaos as rails, overhead wires and signalling fail, and A & E departments overwhelmed by the old, very young, and vulnerable suffering from overheating.”
Prof Richard Allan, Professor of Climate Science, Department of Meteorology, University of Reading, said:
“A heatwave in June is par for the course but temperatures nudging toward 40 degrees Celsius were unprecedented for the UK up until 2022. Whilst May brought record dry heat, this week will see a more muggy heatwave that makes it difficult to stay cool and critical for those with underlying health conditions.
“It is blindingly obvious that heatwaves will increase in severity as rising greenhouse gases stifle the planet’s ability to lose heat to space. A warmer atmosphere’s greater thirst for water also means more rapidly onsetting droughts but also the intensification of extreme rainfall and associated flooding as excess water drained from the soil and oceans is channelled into storms that can often be sparked off by summer heat.
“The reality of global warming talked about when I was young in the 1980s is now playing out, yet the solution to avoid further dangerous climate change remains unchanged – upgrade our industry, transport and agriculture to vanquish greenhouse gas emissions across all sectors of society.”
Prof Liz Bentley, Chief Executive, Royal Meteorological Society, said:
“The coming week will bring an unprecedented heatwave with temperatures likely to reach 38-39°C. The current June record is 35.6°C.
“This will lead to two consecutive months, May and June, in which the UK temperature records have been annihilated by well over 2°C.
“The weather pattern driving this heatwave is due to a high pressure system where the air aloft descends and is compressed leading to significant warming. This is similar to the weather pattern that led to the late May heatwave.
“However one of the overriding reasons we are experiencing more frequent and intense heatwaves is because our climate has changed due to the fossil fuel emissions leading to more dangerous extremes of heat.”
Dr Akshay Deoras, Senior Research Scientist, National Centre for Atmospheric Science & Department of Meteorology, University of Reading, said:
“This is not just a heatwave, it is a heat-dome driven furnace that will grip most of southern UK and push temperatures into truly exceptional territory.
“We are looking at an intense and record-breaking spell of heat with widespread impacts on public health, infrastructure and essential services. Unlike the heatwaves of May 2026 and July 2022, elevated humidity levels are expected to make conditions feel even more oppressive and dangerous by severely reducing the body’s ability to cool itself through sweating.
“Long-standing June temperature records are set to be shattered by 25 June, potentially by a significant margin, and with temperatures edging dangerously close to levels previously thought almost unimaginable in the UK.
“The driving force behind this event is a heat dome, which is a vast area of high pressure parked over the UK and western Europe. Think of it as a giant atmospheric lid, suppressing cloud formation and allowing relentless sunshine to bake the ground day after day. At the same time, air sinking beneath the high pressure compresses and warms, much like air heating up inside a bicycle pump when it is squeezed.
“Human-driven climate change has provided the springboard for this event, loading the atmosphere with extra heat and making extreme temperatures far more intense than they would have been in the past.
“Adding to the concern is the likelihood of widespread tropical nights, where temperatures remain above 20°C after dark. This prevents homes and buildings from cooling down, leaving many people struggling to sleep and reducing the body’s ability to recover from the daytime heat.”
Dr Chloe Brimicombe, Climate Scientist and Heatwave Researcher, University of Oxford, said:
“This period of extreme heat is forecasted to be the first heatwave of the summer in the UK and Central Europe and countries like Algeria in Northern Africa.
“Heatwaves are becoming more likely with climate change. It is possible that for a second month in a row record temperatures could be broken – which is quite alarming. The UK record dates back to the infamous 1976.
“The UK infrastructure is not prepared for heat, but there are lots of solutions to build resilience. This includes prioritising cooling from heat pumps for the most vulnerable such as care home, hospital, and educational settings. Designing heat safe policies with organisations and employees. And understanding how heat increases and planning for that increase in water consumption. A transition to net zero is necessary to stop summers becoming even hotter.”
* https://weather.metoffice.gov.uk/warnings-and-advice/uk-warnings#?date=2026-06-22
Declared interests
Prof Xueyu Geng: “No commercial relationships or other positions.”
John Lawrence: “No conflicts.”
Prof Lucelia Rodrigues: “No conflicts of interest.”
Dr Antonios Kanellopoulos: “I am CEng and CSci, member of the Institute of Materials, Minerals and Mining siting in their Construction Materials Group leadership team. I am also a member of the Institute of Concrete Technology and a senior member of The International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM).”
Prof Hayley Fowler: “Funded by MRC, EPSRC, NERC, UKRI, Royal Society.
Industry funding from Gallagher Re.
Chief editor of frontiers in interdisciplinary climate studies.
Chair of Hadley centre climate programme science and advisory group.
Member of the climate change committee (adaptation).”
Dr Jess Neumann: “None to declare.”
Dr Laurence Wainwright: “No interests to declare.”
Prof John Marsham: “I receive UKRI , NERC, Gates, FCDO and Met Office research project funding.”
Dr Chengzhi Peng: “No conflicts of interest to declare.”
Prof Mujib Rahman: “No interests to declare.”
Dr Mireia Ginesta: “None.”
Anna Harrison: “We have a data product which projects impact of shrink-swell subsidence for use by developers, lenders, insurers etc, which Anna Is involved in developing. This is a BGS project however and not industry funded etc. Otherwise no conflicts.”
Jo Parker: “I am currently working as a contractor for UK Water Industry Research providing project management services. This is a not for profit membership research organisation. I also work as a sub-contractor for a variety of small and medium sized civil engineering contractors providing quality assurance services. I have my own company with my husband as the only other board member. I am also currently board member of a new tech company, OXEMS, although this is in the process of being wound up.”
Prof Guy Gratton: “No relevant interests to declare.”
Dr Heather Massey: “Heather Massey is a in the Extreme Environments Laboratory at the University of Portsmouth and also a member of the Medical Advisory Board of the Ectodermal Dysplasia Society (https://edsociety.co.uk/).”
Anni Feng: “She works at Hoare Lea, a built environment engineering consultancy firm.”
Prof Lizzie Kendon: “None.”
Prof Barbara Rossi: “None.”
Prof Friederike Otto: “None.”
Prof Dann Mitchell: “None.”
Dr Linda Speight: “No conflict of interest.”
Prof Bill McGuire: “Bill McGuire is Professor Emeritus of Geophysical & Climate Hazards at UCL. His new book is The Fate of the World: a History and Future of the Climate Crisis.”
Prof Richard Allan: “No conflicts of interest.”
Prof Liz Bentley: “No conflicts of interest.”
Dr Akshay Deoras: “I’ve no conflict of interest to declare.”
Dr Chloe Brimicombe: “No disclosures.”
For all other experts, no reply to our request for DOIs was received.