The analysis suggests that around 42 per cent of these deaths were linked to the additional heat caused by human-induced climate change.

Researchers estimated that around 550 heat-related deaths occurred in England and Wales during the May heatwave, which lasted from May 21 to 29, while approximately 2,200 deaths occurred during the June heatwave between June 18 and 28.

Both heatwaves shattered long-standing temperature records, with highs of 35.1 degrees Celsius recorded in West London in May and 37 degrees Celsius in East Anglia in June.

The report suggests that human-induced climate change intensified the heatwaves, with daytime maximum temperatures across England and Wales estimated to have been 3 to 4 degrees Celsius hotter than they would have been without additional warming.

Using historical mortality records and established peer-reviewed methods, the analysis builds on previously published research examining the relationship between heat and daily deaths from all causes in England and Wales.

Scotland and Northern Ireland were not included in the analysis as they were not affected by temperatures as extreme as those recorded in England and Wales.

The analysis suggests that the additional heat caused by human-induced climate change was responsible for approximately 59 per cent of estimated heat-related deaths during the May heatwave and 38 per cent during the June event.

South East records highest estimated death toll

Across the May and June heatwaves, the South East of England was estimated to have recorded the highest number of excess heat-related deaths, at 549, followed by London with 453 and the West Midlands with 368.

However, when population size was taken into account, the West Midlands recorded the highest estimated rate during the June heatwave, at 49 deaths per million people.

Researchers said the regional pattern could indicate that people living in areas less frequently exposed to extreme heat may be more vulnerable when unusually high temperatures occur.

Older people were estimated to have been the most severely affected, with those aged over 85 accounting for approximately 60 per cent of total excess heat-related deaths across the two heatwaves.

The findings highlight the growing health risks posed by extreme heat in the UK, particularly as record-breaking temperatures are occurring earlier in the summer season.

Researchers said 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 at 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.”

How researchers conducted the analysis

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 degrees Celsius globally due to human activity — with those in a cooler, pre-industrial climate.

The researchers then used published findings on the relationship between temperature and mortality to estimate heat-related deaths during the two heatwaves in England and Wales.

These estimates were compared with a hypothetical scenario in which the climate had not been warmed by human activities.

The researchers cautioned that the analysis was 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 temperature and mortality risk in each region, based on historical observations.

While these assumptions introduce some uncertainty into the results, researchers said the method has previously produced mortality estimates comparable to those issued by the UK Health Security Agency (UKHSA) for past heat events.

The 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.