Extreme heat during the May and June heatwaves in England and Wales led to approximately 2,700 premature deaths, with about 440 deaths per day during the three-day peak in June, according to scientists at Imperial College London and the Met Office.
Heatwave fatalities and climate change impact
Dr Clair Barnes, who led the analysis at Imperial College London, said: “These are big numbers and we don’t want to see this many people dying. We’ve reached the point where the heat is so extreme that we can’t help but acknowledge the impacts it has.” The study found that more than 40% of the deaths would not have occurred without the 1.4C of human-caused global heating to date.
For comparison, about four people die each day from road traffic collisions and about 35 daily from alcohol and drug use, according to government statistics. The June heatwave was the widest and most intense ever recorded in Europe, estimated to have caused over 20,000 deaths across the continent.
Record-breaking temperatures and warnings
Dr Mark McCarthy of the Met Office noted that 2026 was “exceptional for the two early-season heatwaves in May and June – these smashed records.” A high of 35.1C was recorded in west London during the May heatwave, and three consecutive days of record-breaking June temperatures ended with a recording above 37C in East Anglia. Climate change added 3C to 4C to these temperatures, the researchers said.
The June heatwave peak triggered three successive days of red warnings from the UK Health Security Agency (UKHSA) and the Met Office, warning of danger to life for all, with the young, old, and those with underlying illnesses most at risk.
National scandal and urgent need for action
Denis Fernando of Friends of the Earth called it “a national scandal that the UK remains so dangerously unprepared.” Prof Emma Howard Boyd, chair of the Heat Risk Commission at the London School of Economics, said: “Particularly alarming is that these figures, covering just the first half of the summer, are already approaching the reported toll from the record-breaking heat of 2022… Government cannot afford to treat these figures as an anomaly – they are a warning of the climate we now live in.”
Detailed death toll estimates
The analysis estimated 550 deaths during the May heatwave (21-29 May), with almost 60% attributed to climate change. About 2,200 heat deaths occurred between 18 and 28 June, encompassing the peak 24-26 June period, with 38% linked to global heating. Dr Barnes explained the lower proportion in June: “primarily because the temperatures were so extreme that even without the extra boost from human-caused warming, the heat-related excess mortality would have been very high.”
The UKHSA previously found that more than 10,000 people died in Britain due to summer heatwaves between 2020 and 2024. The Climate Change Committee has warned for over a decade that the UK’s plans to protect people from rapidly worsening extreme weather are inadequate.
Methodology and broader context
The analysis used peer-reviewed methods to examine weather data and climate models, then applied published research linking heat and daily mortality in England and Wales. The fatalities counted are “excess deaths” from all causes, including heart attacks and other medical emergencies provoked by heat. Dr Ross Thompson of the UKHSA said focusing on heat as a direct cause of death “would just be the tip of the iceberg. It really underestimates the total burden of heat.”
Globally, a conservative estimate by medical experts in 2025 concluded that rising heat kills one person per minute on average. The UK’s detailed data makes such analysis possible, but many countries hardest hit by rising temperatures lack this capability.
