An estimated 2,877 people died during heatwaves in May and June, the UK Health Security Agency announced on 30 July, a figure almost double the total for the whole summer in 2025.
The estimate covers only the early part of the summer. The UK saw five back-to-back heatwaves, with temperatures of up to 38.1C recorded in London. August heatwave casualties are still being counted and have yet to be included in published figures.
England is on track to record its highest ever number of heat-related deaths this summer, according to the figures cited by the agency. The eventual total for the 2026 summer season remains unknown.
The mortality figures are estimates rather than observed counts of individual deaths. They are based on the association between mean outdoor ambient temperatures and deaths, and should not be read as direct cause-of-death records for each person included in the total.
Separate figures published by the Office for National Statistics, or ONS, on Wednesday set out the longer-term relationship between temperature and mortality in England and Wales. The analysis does not include the heatwaves seen in 2026.
In the most recent year in the ONS data, there were 2,805 heat-related deaths in England and Wales. The highest annual number of heat-associated deaths in the data was recorded in 2022, when the estimate was 4,652.
Across the 38 years between 1988 and 2025, an estimated 40,063 deaths in England were associated with the hottest days. A further estimated 2,070 deaths in Wales were associated with the hottest days over the same period. The ONS analysis therefore records more than 40,000 heat-related deaths in England and Wales over those years.
Older people faced the sharpest risk in the analysis. Those aged 65 years and over experienced at least a 50 per cent increased mortality risk when temperatures exceeded 24C, compared with optimal temperatures.
London had the highest proportion of deaths attributable to both the hottest and coldest days. The ONS data does not provide a geographic breakdown of the 2026 heatwave estimates.
The analysis also found a substantial toll associated with cold weather. In the most recent year in the ONS data, there were 2,244 cold-related deaths in England and Wales. In England, an estimated 138,944 deaths were associated with the coldest temperatures between 1988 and 2025, representing 0.72% of all deaths.
The early-summer heatwave estimate comes after last year’s warmest summer on record, when the UK experienced four back-to-back heatwaves and a mean temperature of 16.12C. In 2026, England has recorded a mean summer temperature of 18.19C so far.
The available figures point to a high mortality burden during periods of extreme temperature, especially among older people. They do not yet provide a final death toll for the 2026 summer, and the ONS dataset cannot be used to assess the heatwaves seen this year because its analysis ends in 2025.
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