Extreme heat led to about 440 deaths per day during the three-day peak of the June heatwave in England and Wales, scientists have estimated. Across the June and May heatwaves combined, approximately 2,700 people lost their lives prematurely, according to analysis led by Dr Clair Barnes at Imperial College London.
Impact of Climate Change on Heatwave Deaths
More than 40% of those affected would not have died without the 1.4C of human-caused global heating to date, the analysis found. For comparison, about four people die each day from road traffic collisions and about 35 a day from alcohol and drug use, according to government statistics.
Dr Barnes 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.'
Record-Breaking Heatwaves
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. The June heatwave was the widest and most intense ever recorded in Europe, estimated to have cost more than 20,000 lives continent-wide. In Germany, almost 5,500 people died, with a record high of 41.7C set.
Dr Mark McCarthy at the Met Office said 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 May, and three consecutive days of record-breaking June temperatures ended with above 37C in East Anglia. Climate change added 3C to 4C to these temperatures, the researchers said.
Urgent Need for Preparedness
Denis Fernando at Friends of the Earth said: 'It’s a national scandal that the UK remains so dangerously unprepared.' Prof Emma Howard Boyd, chair of the Heat Risk Commission, added: '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.'
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 UK plans to protect people from worsening extreme weather are inadequate.
Details of the Analysis
The analysis estimated 550 heat-related deaths during the May heatwave (21-29 May), with almost 60% attributed to climate crisis. About 2,200 heat deaths occurred between 18 and 28 June, including the peak 24-26 June period, with 38% attributed to global heating.
Dr Barnes noted the lower proportion for 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 study used peer-reviewed methods to analyze weather data and climate models, then applied published research linking heat to daily mortality across England and Wales. The estimated fatalities are 'excess deaths' from all causes, including heart attacks and other medical emergencies provoked by heat. Dr Ross Thompson at UKHSA said focusing on heat as a direct cause of death 'would just be the tip of the iceberg' and would 'underestimate the total burden of heat.'
Extreme temperatures will worsen as fossil fuel burning continues, making emissions cuts and protective measures urgent. Dr Barnes emphasized: 'We can stop making it worse by transitioning towards net zero, because that is not a political target, it’s a physics-based target.'
