An estimated 2,700 people died prematurely during the UK heatwaves in May and June, with scientists warning that human driven climate change played a major role in the death toll.

Researchers found that the three hottest days of the June heatwave claimed around 440 lives each day across England and Wales. Across both the May and June heatwaves, thousands of excess deaths were recorded as soaring temperatures placed increasing pressure on vulnerable people.

The analysis suggests that more than 40 per cent of those deaths would not have happened without the 1.4C of global warming caused by human activity. Scientists say rising greenhouse gas emissions are making heatwaves both more frequent and more intense, increasing the risk to public health.

Dr Clair Barnes of Imperial College London, who led the research, said the scale of the deaths should serve as a warning.

She said the UK has reached a point where extreme heat can no longer be treated as an occasional inconvenience, adding that its impacts are now impossible to ignore.

During the height of the June heatwave, the UK Health Security Agency and the Met Office issued three consecutive red heat health alerts, warning that the temperatures posed a danger to everyone, not only those who are elderly or have underlying health conditions.

Previous figures published by the UK Health Security Agency estimated that more than 10,000 people died because of summer heatwaves across Britain between 2020 and 2024. The Climate Change Committee has also repeatedly warned that the UK remains poorly prepared for increasingly severe weather driven by climate change.

The June heatwave was the most widespread and intense ever recorded across Europe and is estimated to have contributed to more than 20,000 deaths across the continent. Germany alone is thought to have recorded almost 5,500 heat related deaths after temperatures reached a record 41.7C.

Scientists say reducing greenhouse gas emissions remains essential to limiting future warming, while governments must also improve measures to protect people during periods of extreme heat.

Dr Mark McCarthy from the Met Office said 2026 had been an exceptional year, with record breaking heatwaves arriving unusually early in the season.

Temperatures reached 35.1C in west London during the May heatwave before climbing above 37C in East Anglia during the June event. Researchers estimate that climate change added between 3C and 4C to the temperatures experienced during the heatwaves.

McCarthy said there is overwhelming evidence that climate change is making heatwaves more common and more intense across the UK, with extreme temperatures rising much faster than average temperatures. He warned that next summer could be even hotter if a major El Niño event develops.

Environmental groups said the findings should be a wake up call.

Friends of the Earth described the UK’s lack of preparedness as a national scandal, while Professor Emma Howard Boyd, Chair of the Heat Risk Commission, warned the figures should not be dismissed as an isolated event.

She said the deaths recorded during just the first half of the summer are already approaching the toll seen during the record breaking heatwave of 2022 and argued they reflect the new climate reality the UK now faces.

Researchers estimate that around 550 people died during the May heatwave between 21 and 29 May, with almost 60 per cent of those deaths linked to the additional warming caused by climate change.

A further 2,200 people are thought to have died during the June heatwave between 18 and 28 June. Around 38 per cent of those deaths were attributed to human caused global warming.

Scientists explained that the proportion linked to climate change was lower in June because temperatures were already so extreme that a large number of heat related deaths would have occurred even without additional warming.

The study combined weather observations, climate models and previous research on the relationship between heat and mortality to estimate how many lives were lost because of extreme temperatures. Researchers also compared today’s climate with a hypothetical world that had not experienced human caused global warming.

Rather than counting deaths where heat was listed as the direct cause, the study measured excess deaths, which include fatalities from conditions such as heart attacks, strokes and other medical emergencies that are triggered or worsened by high temperatures.

Health experts say this provides a much more accurate picture of the true impact of extreme heat, as heat itself is rarely recorded on death certificates despite contributing to thousands of deaths each year.

While the UK has detailed records that allow researchers to estimate heat related deaths, scientists warn that many countries do not have the same data. A separate global assessment published in 2025 estimated that rising temperatures now contribute to the death of around one person every minute worldwide.