A rapid attribution study by Imperial College London, the UK Met Office and the London School of Hygiene and Tropical Medicine has estimated that more than 2,700 people in England and Wales died from heat-related causes during record-breaking heatwaves in May and June 2026. More than two-fifths — approximately 42% — of those estimated deaths were attributed to the additional heat caused by human activity, primarily the burning of fossil fuels [Source: The Ecologist].
The researchers broke down their estimates by event: roughly 550 people are estimated to have died from heat-related causes across nine days of the May heatwave, with approximately 2,200 deaths estimated over 11 days surrounding the June heatwave. The study examined the May event, when temperatures peaked at 35.1°C, and the June heatwave, which exceeded 37°C and was accompanied by high humidity. Highs of 37.7°C were recorded on 26 June at Lingwood, Norfolk, amid numerous red health heat alerts across England.
Mark McCarthy, science manager of the UK Met Office's climate attribution team, said the heatwaves were extreme for the UK and western Europe and were particularly exceptional for their timing and how early in the year they occurred [Source: RTE]. Researchers used weather data, climate models and heat-related deaths research to estimate deaths and compare them against a modelled climate not warmed by human activities. The figures are modelled estimates rather than confirmed death registrations, which is standard methodology for rapid attribution studies.
2026 has become a record year for the most days to reach 34°C or higher in a calendar year, surpassing the previous record of seven days set in both 1976 and 2020. The UK's record for the hottest day in May was also broken on 25 May 2026, when 34.8°C was recorded at Kew Gardens in London, exceeding the previous May record of 32.8°C set in 1922. For context, estimates for summer 2025 placed UK heat-related deaths at 1,504, according to the UK Health Security Agency [Source: AOL/PA]. During a comparable period in July 2022, the UK recorded 2,227 excess deaths — 10.4% above the average for that period — according to the Office for National Statistics and the UK Health Security Agency [Source: NCBI/PMC]. The World Health Organization has recommended that authorities in Europe plan for extreme heat in the same way they do for winter flu.
Sources: Sky News, BBC News, Bloomberg, RTE, The Ecologist, AOL/PA, NCBI/PMC