Rapid analysis suggests climate change is responsible for around 42% of total heat-related deaths across May and June heatwaves
More than 2,700 people are estimated to have died from heat-related causes during the record-breaking May and June 2026 heatwaves in England and Wales, according to a new rapid analysis led by researchers from the London School of Hygiene & Tropical Medicine (LSHTM), Imperial College London and the Met Office.
The analysis suggests that around 42% of these deaths were due to the additional heat caused by human-induced climate change.
Researchers estimate that around 550 heat-related deaths occurred in England and Wales during the May heatwave, which took place between 21 and 29 May 2026, and around 2,200 during the June heatwave, from 18 to 28 June 2026.
Both heatwaves broke long-standing temperature records, with highs of 35.1°C recorded in West London in May, and 37°C in East Anglia in June. The report suggests that the heatwaves were intensified by human-induced climate change, estimating that daytime maximum temperatures across England and Wales were 3-4°C hotter than they would be without this additional warming.
Using historical mortality records and established peer-reviewed methods, this research builds on previously published research on the relationship between heat and the number of daily deaths from all causes in England and Wales. Scotland and Northern Ireland were not included in the analysis because they were not affected by temperatures as extreme as those recorded in England and Wales.
The analysis suggests the extra heat caused by human-induced climate change was responsible for approximately 59% of estimated heat-related deaths in May and 38% in June.
Across the May and June heatwaves, the South East of England is estimated to have the highest number of excess heat-related deaths, with 549 in total, followed by London with 453, and the West Midlands with 368. However, when population size is taken into account, the West Midlands had the highest estimated rate during the June heatwave, at 49 deaths per million people.
Researchers suggest this regional pattern could indicate that people in areas less frequently exposed to extreme heat may be more vulnerable when unusually high temperatures occur.
Older people were also estimated to be most affected, with those aged over 85 accounting for approximately 60% of total heat-related excess deaths across the two heatwaves.
The findings highlight the growing health risks of extreme heat in the UK, particularly as record-breaking temperatures are now occurring earlier in the summer season. Researchers say the results underline the urgent need to adapt homes, workplaces and public infrastructure to hotter conditions, alongside global efforts to reduce greenhouse gas emissions.
Dr Malcolm Mistry, Assistant Professor in Climate and Geo-spatial Modelling in the Environment and Health Modelling Lab at LSHTM, said: "We are still in the first half of summer in the UK and large parts of England and Wales have already experienced two record-breaking heatwaves, in May and June, triggering extreme heat-health alerts across England. With climate change driven by human activity making summer heatwaves more frequent and more intense, these spikes of extreme hot weather are rapidly evolving into a major health risk for people in the UK.
"It is vital that action on adapting Britain's homes, workplaces, and critical infrastructure to extreme heat outpaces these health risks, especially if we are to protect those most vulnerable to its impacts, such as older people, babies, and children."
Dr Clair Barnes, Research Associate in Extreme Weather and Climate Change, Imperial College London, said: "It's time we woke up to the fact that we now live in a country with dangerously hot summers. To protect people during future extremes, we must urgently adapt to the reality of the climate we now have, and double down on global efforts to reach net zero emissions to stop this from getting worse."
Dr Mark McCarthy, Manager of Climate Attribution at the Met Office, said: "2026 has been exceptional for the two early season heatwaves in May and June. These have smashed records that had stood from May 1944 and June 1976 respectively. For the time of year these events were extreme, even in our warmer climate."
To assess the role of climate change in the May and June heatwaves, the research team analysed weather data and climate models to compare temperatures in today's climate, which has warmed by approximately 1.4°C globally due to human activity, with a cooler pre-industrial climate.
They then used published findings on the relationship between temperature and mortality to estimate heat-related deaths during the two heatwaves in England and Wales, and compared this with a hypothetical scenario in which the climate had not been warmed by human activities.
The researchers note that the analysis is based on modelled estimates rather than observed mortality data. The approach includes assumptions about the number of people exposed to heat and the relationship between temperatures and mortality risk in each region, based on historical observations. These assumptions introduce some uncertainty into the results, but the method has been found to produce mortality estimates comparable to those issued by UKHSA for past heat events.
UKHSA is expected to publish an official interim analysis of the heat-associated mortality impacts of the recent heatwaves, based on observed mortality data, in the coming weeks.
This story is based on an original press release by the Grantham Institute - Climate Change and the Environment, Imperial College London.
Publication
Read the rapid analysis, entitled 'UK climate heat health risks May and June 2026', on the Grantham Institute website.
