Thousands May Have Died in Record UK Heat Waves

More than 2,700 people may have died from heat-related causes during the UK's exceptionally hot weather in May and June, according to estimates by researchers from Imperial College London, the Met Office and the London School of Hygiene and Tropical Medicine.

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Scientists Estimate Thousands Died During Record UK Heat

The estimate is based on modelling using previous death records and existing knowledge about the health impacts of extreme heat, rather than confirmed mortality data.

Researchers believe most of the deaths occurred during June, which became the warmest June on record in England. Temperatures reached 37.7C at Lingwood in Norfolk, surpassing the previous June record of 35.6C set in 1957.

A rare red heat alert was issued across parts of England and Wales during the June heatwave, warning that the extreme temperatures posed a significant risk to life, including for healthy people.

Record Temperatures Fuelled by Heat Dome

May also saw record-breaking temperatures, with the mercury reaching 35.1C at Kew Gardens on 26 May. That exceeded the previous May record of 32.8C, first set in 1922 and matched in 1944.

Scientists said both heatwaves were driven by a "heat dome" – a persistent area of high pressure that trapped hot air over the UK.

The researchers said human-caused climate change intensified the heat, with global warming of around 1.4C since pre-industrial times adding an estimated 3C to 4C to peak temperatures during the two heatwaves.

High overnight temperatures and humid conditions, particularly in June, also prevented many people from cooling down, increasing the health risks.

Extreme Heat Poses Serious Health Risks

Experts warned that prolonged exposure to extreme heat places significant strain on the body, especially when dehydration occurs. The heart must work harder to regulate body temperature, increasing the risk of heart attacks, strokes and other potentially fatal medical emergencies.

Older people, babies and those with existing health conditions remain among the most vulnerable, although researchers stressed that dangerous heat can affect anyone, including otherwise healthy individuals.

Extreme heat is often described as a "silent killer" because early symptoms can be difficult to recognise before serious illness develops.

Many homes across the UK are also poorly designed to cope with sustained high temperatures, leaving residents more exposed during prolonged heatwaves.

More Frequent Heatwaves Expected

The researchers emphasised that their estimate is based on statistical modelling and may differ from the eventual official figures.

Dr Clair Barnes, an expert in extreme weather and climate change at Imperial College London, said the estimates were intended to raise awareness of the dangers posed by extreme heat. She said if greater public awareness leads people to better protect themselves during future heatwaves, even if the estimates prove too high, that would be a positive outcome.

Researchers noted that predicted heat-related deaths in 2025 ultimately proved to be about half of the expected 3,039 fatalities, with heat health alerts and action by the NHS and care system believed to have reduced the impact.

Scientists also warned that, without stronger action to cut greenhouse gas emissions and improve adaptation measures, heat-related deaths in parts of northern Europe could approach those caused by cold weather within the next few decades. They added that heatwaves are expected to become more frequent, longer-lasting and more intense as global temperatures continue to rise.

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13 July 2026

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