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Scientists comment on the UK heatwave.
Dr Shona Koren Paterson, Director of Global Lives Research Centre, Brunel, University of London:
“We all know that heatwaves and extreme heat events are only going to become more prevalent in the coming years which will lead to more impacts and heat-related mortality. There are also the cascading impacts to be aware of, impacts on water availability, on transport links and on the usability of certain buildings. Mental health is perhaps the least talked about health impact under heat conditions. Extreme heat can exacerbate existing symptoms of depression, anxiety and stress in addition to physical symptoms.”
Dr Akshay Deoras, Research Scientist, National Centre for Atmospheric Science & Department of Meteorology, University of Reading, said:
“As of the afternoon of 30 June, the high-pressure system driving the current heat dome is centered near Denmark, placing the UK on its western edge. This heat dome is bringing stable, mostly cloudless weather and drawing in hot, dry air from the south. Whilst the heat dome is responsible for the ongoing heatwave in Europe, anthropogenic climate change is likely intensifying it. The Earth is now significantly warmer than what it used to be in the past, which increases the possibility of witnessing heatwaves whenever heat domes form during the summer. Besides, such extreme heat events are becoming more frequent and severe due to climate change. Attribution studies will help clarify how much climate change has increased the likelihood of the current heatwave in Europe.
“Heatwaves are deadly. They disproportionately affect vulnerable groups—older adults, young children, people with chronic illnesses, and those without secure housing. Prolonged heat can overwhelm the body’s ability to regulate temperature, leading to dehydration, heat exhaustion, and potentially fatal heatstroke. With dry land surface conditions, the risk of wildfires—like those currently seen in Greece—also rises. We need to treat extreme heat with the same seriousness we give to dangerous storms. Avoid outdoor activity during the hottest parts of the day, stay hydrated even if you’re not thirsty, and avoid alcohol. Wear loose, light-coloured clothing and a wide-brimmed hat if going outside. If you feel dizzy, nauseous, or experience a rapid heartbeat or headache, get to a cool place, hydrate, and cool your body down—these symptoms can quickly become life-threatening.”
Dr Ben Clarke, Research Associate in Extreme Weather and Climate Change Centre for Environmental Policy, Imperial College London, said:
“We have a huge body of evidence that the current heatwave was made significantly hotter by global warming, so we don’t need more attribution studies to state this. Just last week World Weather Attribution undertook a very rapid analysis and found that the heatwave was made about 2-4 degrees hotter due to global warming (or, equivalently, about 100 times more likely).
“The best way to think about summer heat in relation to climate change is first to say that without climate change, we would still experience periods of fine warm weather in June – that’s normal. However, a hotter atmosphere means that what would have been a period of fine weather is now very hot. While this is still reasonably safe for most of us, as long as we stay well hydrated and in the shade, it becomes dangerous for the most vulnerable in society – particularly the elderly, and those with pre-existing cardiovascular and respiratory health conditions.
“In short, climate change is making ‘nice’ weather more dangerous, and already dangerous weather more deadly. And as long as we keep burning fossil fuels for energy, heatwaves like this will keep getting more intense, showing that the cost of this energy to all of us does not stop at our bills.”
Prof Hugh Montgomery, Professor of Intensive Care Medicine, University College London, said:
“In the shorter term, heatwaves can be lethal, especially to the old, young; to those who for any reason cannot escape the heat; to those with other illnesses (as those diseases can make them especially vulnerable, as can the medications they take, and can affect the stability of some medicines if exposed to heat.) Those working manually generate even more heat, and are also at greater risk- especially if they cannot seek shade or maintain a fluid intake to cope with sweat loss. These impacts will worsen as heatwaves do, but the societal impacts on health (including economic impacts, food shortages and rising food prices, and mass migration) accelerate over coming years.
“As a doctor working with the critically ill, I know that delaying action when severe symptoms appear can be fatal. We must likewise take action on Climate Change now, not just treating those symptoms, but their cause.”
Dr Garyfallos Konstantinoudis, Research Fellow at the Grantham Institute – Climate Change and the Environment, Imperial College London:
“Heatwaves are silent killers. Unlike floods or storms, their impact can be invisible: people who die during extreme heat usually have pre-existing health conditions, and heat is rarely recorded as a contributing cause of death. This makes the true toll of heatwaves both underestimated by the public and difficult to measure directly.
“The 2025 heatwave is strikingly comparable to 2022 in its atmospheric dynamics and early-season severity. But its ultimate health toll—measured via excess deaths—won’t be clear until after the season ends.
“The total mortality toll of the extreme heat in summer 2022 in Europe was 61,672 (CI: 37,684-86,807) and approximately half of these deaths were attributed to human induced climate change.
“The evidence is unequivocal: unless strong mitigation and adaptation measures are implemented, most European cities will face rising heat-related mortality.”
Prof Elizabeth Robinson, Professor of Environmental Economics and Acting Dean at Global School of Sustainability, said:
“The impacts of heat on health are increasingly well documented. Perhaps less understood is how workers are harmed by health. Workers who are particularly vulnerably include those who work in high exposure sectors such as agriculture and construction, those who have particularly precarious contracts and do not feel empowered to adjust their working patterns to protect their health, and those who work in the “gig economy” and may have to choose between protecting their health and protecting their income.
“Recent research that I led (https://www.lse.ac.uk/granthaminstitute/publication/improving-the-resilience-of-the-uk-labour-force-in-a-1-5c-world/) finds that even during hot periods where temperatures and duration of heat are not sufficient for a heatwave to be declared, such as in late July 2024 in the UK, workers reported symptoms of heat stroke or heat exhaustion, such as headaches or dizziness.
“Early warning systems work. In our paper we show that during this 2024 UK period of heat, alerts reduced the probability of workers reporting adverse health effects from the heat by approximately 5 percentage-points. But early warning systems need to be implemented in parallel with more investment in adaptation and broader worker protections.”
Dr Malcolm Mistry, Assistant Professor in Climate and Geo-Spatial Modelling at the London School of Hygiene & Tropical Medicine (LSHTM), said:
“Every individual extreme weather event requires its own formal evaluation to determine how likely or intense the event would have been in a pre-industrial climate.
“However, researchers have carried out several similar analyses in recent years and have established a strong link between the human-induced climate change and extreme weather events, especially for heatwaves across several parts of Europe. The results show that heatwaves continue to increase in frequency, duration and intensity across many parts of the globe, and this change is driven largely by human-induced climate change. Importantly, heatwaves occurring in late spring or in early part of summer, both in the northern and southern hemispheres are also being observed in recent years with studies highlighting a link to climate change.
“Heatwaves, as many other weather extremes, do exist in a natural climate system, and are not unusual in a given year as our planet has a ‘natural variability’. There can be natural cycles affecting the intensity, duration and frequency in a season, or even over a few years.
“However, with every degree increase in human-induced warming, there is more energy being added to the climate system, thereby disturbing its natural equilibrium. This added energy can not only affect how high temperatures can reach in a specific heatwave, described as its intensity, but also how long the heatwave can last and how often can a place experiences a heatwave on average, known as their duration and frequency, respectively.
“What are the impacts of heatwaves on:
“Health: Excess deaths from heat have been well documented in scientific research, with the most vulnerable population being the elderly (generally above 65 years), infants and people with pre-existing health conditions (e.g., diabetes, kidney and heart disease). Risks of heat exposure during pregnancy are also well studied.
“Outdoor workers such as farmers, construction and postal delivery workers, athletes undertaking strenuous activity, rough sleepers and residents in care facilities are all at high risk during heatwaves and should have access to support.
“In addition to the potential effects on health, heatwaves can also impact healthcare systems, with an increase in calls to ambulance and emergency services. Power blackouts or complete failures of energy infrastructure during heat waves can affect public health infrastructure, as well as transport systems such as train networks.
“Agriculture: Heat stress has a detrimental effect on crop productivity. Most crops require an optimum range of temperatures between 10-30 degrees Celsius C, along with moisture or water either as natural rainfall or irrigation to reach nutritious levels. Heatwaves can have a damaging effect on crops irrespective of the timing of the crop growing season. Similarly, it can also exacerbate soil moisture and droughts, thus affecting the wider flora and fauna.
“Energy: Usage of air conditioning to maintain thermal comfort levels indoors has risen energy demand, especially during peak daytime hours when the temperatures are highest, which in turn can result in potential blackouts if the energy infrastructure is incapable of coping with the demand load.
“What can be done in terms of long-term planning (apart from the obvious and more urgent need to mitigate climate change):
“Green spaces, better quality housing, temporary cooling centres in heat-prone areas and portable relief centres are all examples of measures that could be adopted to help protect communities. In future, large scale events in outdoor public places may also need better planning, perhaps rescheduling outside peak summer months to protect attendees from the potential effects of extreme heat.”
Prof John Marsham, Professor of Atmospheric Science, University of Leeds, said:
“We know that climate change makes heatwaves in the UK more likely and more intense, with a recent study showing that 40 degrees C in the UK is now approximately a 1 in 24 year event for the UK, and 45 degrees is now possible: this will continue to get worse until we have essentially phased out fossil fuels and reach net-zero. We can clearly say that the ongoing heatwave has been made more likely by climate change (caused by burning of fossil fuels), even if calculating the increase in likelihood will take some time.”
Dr Josh Foster, a Lecturer in Environmental Physiology at King’s College London, said:
What are the health impacts of extreme heat?
“The health impacts of extreme heat are vast. During the 2022 heatwave, which lasted about 2 weeks, over 5,000 people over the age of 70 died prematurely. Many studies show that heat exposure increases the risk of heart attacks, kidney failure, and even sepsis. Alarmingly, extreme heat is also associated with a dramatic rise in mental health outcomes in people of all ages.”
Who is most at risk of the health impacts of extreme heat?
“People over the age of 70 are the most vulnerable population during extreme heat events. However, the risk is strongly associated with general health. People who have mobility issues, chronic diseases (cardiovascular, respiratory or kidney), or those taking certain medications (diuretics, beta blockers, psycholeptics) are the most at-risk populations. From a more practical perspective, those who lack access to cooling (air con, fans), or those who have poor social contact and care, are also vulnerable.”
Why do our bodies react to extreme heat?
“Heat can place significant stress on the body. Our most immediate response is to move blood from the core toward the skin, allowing greater heat loss to the environment, and for blood to be cooled by sweating. This response, however, places stress on the heart, as it needs to work harder to help maintain blood pressure. Furthermore, during heat exposure, we deliver less blood to the centre of the body, reducing oxygen delivery to the gut and kidneys. Over time this lack of oxygen supply can damage these organs, leading to very serious complications. The stress on our body is made worse with dehydration and high body temperatures.”
Prof Paul Hunter, Professor in Medicine, University of East Anglia (UEA), said:
“During heat waves we frequently see a peak in deaths not all of which are reports as being heat deaths. In the summer of 2023, there were an estimated 2,258 to 3,712 deaths associated with 5 heat episodes. You could see this even in deaths recorded as due to covid. Heat waves are also linked to increased hospitalisations.
“Those most at risk of dying during a heat wave are:
“To protect yourself during a heat wave
“It is important that if we know of elderly people who are isolated, and unable to go out that we ensure they are well and have enough to drink and that they are drinking.
“If you or someone is feeling unwell with the heat, drink plenty take cool showers of mop skin with a cold flannel. Remove unnecessary clothing.
“If not getting better and if body temperature is high call 111.”
Prof Manoj Joshi, Professor of Climate Dynamics, UEA, said:
“For any heatwave, or indeed any extreme event, it’s not about whether or not it’s a direct result of climate change, but what the likelihood is of such an event, for instance in terms of duration and/or severity, in the present and future, compared to its likelihood say 50 or 100 years ago.”
Dr Neven Fučkar, Climate Scientist, Environmental Change Institute, University of Oxford, said:
“The current extreme temperature conditions in many parts of the UK are related to the heat dome over continental Europe encompassing the Iberian Peninsula, France, and the most of Alpine region. Also, the high-pressure system centred on the Netherlands contributes to intense southerly flow or warm and moist air over the UK and Ireland. This atmospheric structure is controlled primarily by mid-latitude weather dynamics, while climate change likely exerts the influence on intensity and/or probability of such extreme temperature event, but to estimate to what extent this requires an event attribution analysis (this can take from few days to few months depending on the scope and details of attribution analysis). The current heatwave does meet the UKHSA temperature thresholds – consecutive three days of daily temperature maximum at or above 25 °C (e.g. Scotland) to 28 °C (e.g. London) – in parts of the UK, hence vulnerable population groups would likely require public health service more than usual in these regions.”
Prof James Dyke, Assistant Director of the Global Systems Institute at the University of Exeter, said:
“These latest European heatwaves are the result of record breaking greenhouse gas emissions. Europe is the fastest warming continent as a result of human caused climate change. The only way to avoid even more extreme heat is to rapidly phase out fossil fuels.”
Dr Raquel Nunes, Associate Professor in Health and Environment, University of Warwick, said:
“Heatwaves are not just periods of hot weather, they are serious public health emergencies that can be deadly, specifically for vulnerable groups such as older adults, children, individuals with chronic illnesses, and those facing poverty, social isolation, or homelessness. Reducing harm requires strong preparedness: early warning systems, clear public advice, and resilient healthcare services. Health professionals play a vital role in recognising risks and supporting patients, while individuals must follow evidence-based guidance such as staying hydrated and checking on others. However, personal actions alone are not enough. Heatwaves expose weaknesses in housing, healthcare, and social systems, demanding long-term planning and a collective, equitable, and just response.”
Dr Jess Neumann, Associate Professor in Hydrology, University of Reading, said:
“The impacts of heatwaves are wide-ranging – some are direct and potentially very severe such as heat exhaustion or heatstroke. However, the effects of heat are not always so obvious or immediate, for example dehydration, lethargy, headaches, or trapped air pollutants which can affect all of us.
“People with respiratory, cardiovascular or other underlying health conditions, babies, small children and other vulnerable groups are particularly at risk, but none of us are immune and we must look after ourselves to stay safe and well.
“Don’t underestimate the heat – drink plenty of fluids, stay out of the direct sun, seek shade and cooler areas, avoid exercising, apply suncream if in the sun and wear appropriate clothing.
“Don’t wait until you are thirsty – drink plenty and regularly.
“Effects of prolonged heat on the environment includes increased risk of wildfires, water evaporation leading to falling river and reservoir levels and increased pollution in water sources. Wildlife including birds, mammals and insects can die if they cannot find access to freshwater so consider filling bird baths, or leaving shallow dishes of water for wildlife in your garden.”
Prof Richard Allan, Professor of Climate Science, University of Reading, said:
“The UK is on the edge of a large dome of heat encompassing continental Europe which is briefly causing heatwave conditions to affect southern Britain as June turns to July. Ocean temperatures are also up to 2 degrees Celsius above average across the waters to the southwest of the UK and hotter still in the western Mediterranean. The ebb and flow of gigantic atmospheric waves have generated the stable, cloud-free conditions for heat to build up across Western Europe. But rising greenhouse gas levels due to human activities are making it more difficult for Earth to lose excess heat to space and the warmer, thirstier atmosphere is more effective at drying soils, meaning heatwaves are intensifying, with moderate heat events now becoming extreme. The severity of summer heatwaves, but also extremes of dry as well as wet weather events, will continue to worsen until we rein in our greenhouse gas emissions and stabilise our warming climate.”
Dr Radhika Khosla, Associate Professor at the Smith School of Enterprise and Environment, University of Oxford, said:
“Populations in urban areas like London are particularly susceptible to extreme heat as the concrete and asphalt absorb and re-emit the sun’s radiation, amplifying its impact on our bodies. For this reason, outdoor workers are particularly at risk and should take regular breaks to hydrate in the shade.
“Soaring temperatures will see a corresponding rise in demand for cooling systems like air conditioning, which can put a strain on our energy infrastructure. Air conditioning and other cooling systems become crucial to maintaining health, productivity and quality of life amidst rising temperatures. However, access to cooling is unfortunately rarely equal even in developed countries, and the UK’s most disadvantaged people will bear the brunt of this heatwave.”
“Over-reliance on air conditioning creates a negative feedback loop: more fossil fuels are burnt to power more air-con units, which in turn worsens climate change and raises global temperatures. Use of fans, shade, green spaces and natural ventilation can all help to reduce air conditioning usage. When we have to rely on air-con, it is important to make sure the systems we are using are the most energy efficient.”
Dr Laurence Wainwright, Departmental Lecturer at the Smith School of Enterprise and the Environment, University of Oxford, said:
“While news coverage of hot weather usually includes images of sunbathing and ice creams, an often-overlooked consequence of heatwaves is their negative impact on our mental health and behaviour. Violent incidents increase, depression worsens and the effect of psychiatric medications on our body can be altered. For every 1°C increase in monthly average temperature, mental health-related deaths increase by around 2.2%. Spikes in relative humidity also result in a higher occurrence of suicide. Learning to adapt to the increasing frequency of heatwaves brought by climate change will mean taking account of all its impacts – including on our state of mind.”
Dr Chloe Brimicombe, Climate Scientist, Royal Meteorological Society, said:
“We are yet to have an attribution study, the heatwave earlier in June in the UK was 100 times more likely with Climate Change. In general we can say the heatwaves and hot spells in the summer are increasing in duration, how often they occur and intensity, how hot temperatures get to. We also think they are growing in area so more people are exposed every time they occur.
“Beyond heat killing people. They cause a rise in hospitalisations especially in the vulnerable groups to heat. In some parts of Europe it has been shown that exposure to extreme heat can raise the likelihood of preterm births and also lower birth weight babies with developmental delay. It can change how long people breastfeed for. In the long term instances of kidney disease also rise.
“We know it can cause a rise in psychosis and suicides. And an increase in small level crime.
“It puts pressure on power grids. Roads melts, railway tracks can overheat, there are signal failures. It puts pressure on the food supply chain and refrigerated lorries. It also can cause a reduction with dry conditions in crops and sunburn in apple and grapes.
“It can reduce appetites, it also can reduce productivity if proper work-rest schedules aren’t in place.
“Shopping patterns change. With less people going shopping or shopping for different products at different times.
“It impacts every part of our society. It will continue to increase unless we transition to net zero and how fast we do this also impacts how much worse these events will get.
“I think it is important that proper early warning systems that save lives are designed to be supported by other policy areas such as urban design and improving critical infrastructure. They should be integrated into our societal system better.”
Dr Friederike Otto, Associate Professor, Centre for Environmental Policy, Imperial College London, said:
“We absolutely do not need to do an attribution study to know that this heatwave is hotter than it would have been without our continued burning of oil, coal and gas. Countless studies have shown that climate change is an absolute game-changer when it comes to heat in Europe, making heatwaves much more frequent, especially the hottest ones, and more intense. Heatwaves are called the silent killer, for a reason, every year thousands of people in Europe die due to extreme heat, particularly those that live in poorly insulated homes, on busy, polluted roads, and that have already health problems. But extreme heat also leads to agricultural losses, infrastructure failure and puts a big strain on plants and animals. To stop people from dying in ever larger numbers we need to stop burning fossil fuels, but we also need to adapt.”
Dr Michael Byrne, Reader in Climate Science, University of St Andrews, said:
“Heat domes – the cause of this week’s European heatwave – are nothing new. They have always happened and always will happen. Heat domes occur when high pressure weather systems, normally lasting a few days, get stuck in place for a week or more. When this atmospheric ‘blocking’ happens in summertime, heatwaves occur. But what is new are the temperatures heat domes deliver: Europe is more than 2 degrees Celsius warmer than in pre-industrial times, so when a heat dome occurs it drives a hotter heatwave.
“Some research suggests heat domes will become more common as climate warms, with more frequent heatwaves as a result. There is large uncertainty regarding the future of heat domes, with no scientific consensus yet. But what is crystal clear is that climate change is loading the dice such that when a heat dome does occur, it brings hotter and more dangerous temperatures.”
Dr Leslie Mabon, Senior Lecturer in Environmental Systems, The Open University, said:
“The extreme high temperatures we are seeing in the UK are being exacerbated by the same phenomenon that is causing the heat dome across Europe. The ‘heat dome’ happens when an area of high pressure air stays over the same area for days or weeks, trapping hot air below it which then expands outwards like a dome.
“In the UK, heat-related illnesses, greater risk for this with pre-existing conditions, and wildfires can all come about because of heatwaves. This is another reminder that climate change makes extremes like this more frequent or intense.”
Declared interests
Dr Ben Clarke: No declarations
Prof Hugh Montgomery: I’m co-chair of the lancet Countdown on Health and Climate Change. I also run the charity-funded non-profit ‘Real Zero’.
Dr Garyfallos Konstantinoudis: No declarations
Dr Malcolm Mistry: NO COI
Prof John Marsham: receives funding from UKRI, NERC and Met Office
Prof Paul Hunter: No declarations
Prof James Dyke: No interests to declare
Dr Raquel Nunes: I have no conflicts of interest.
Dr Jess Neumann: Dr Jess Neumann is a Trustee of River Mole River Watch Charity and works with the Environment Agency in this role.
Prof Richard Allan: No conflicting interests
Dr Radhika Khosla:No declarations
Dr Laurence Wainwright: No declarations
Dr Chloe Brimicombe: No declarations
Dr Friederike Otto: No declarations
Dr Michael Byrne: No declarations
Dr Leslie Mabon: Leslie Mabon is an Ambassador for Scotland’s National Centre for Resilience. This is a voluntary position, committed to ensuring that government, industry and society are able to make decisions about resilience that are informed by the best available evidence.
For all other experts, no reply to our request for DOIs was received.