More than 40,000 people died of climate-related causes over the 38 years between 1988 and 2025 in England and Wales, according to new estimates by experts.
The figures, published by the Office for National Statistics (ONS) on Wednesday, show the the proportion of deaths associated with the hottest days has increased in recent years, and that the gap between heat and cold-related deaths is also closing.
London had the highest proportion of deaths attributable to both the hottest and coldest days, according to the research, and those over 65 were most at risk in both extremes.
The statistics do not include this year’s heatwaves, which have put the UK on track for its hottest summer on record as the country sweltered in five back-to-back heatwaves, with temperatures of up to 38.1C recorded in London.
Researchers looked at the daily mean temperatures from 38 years of climate and mortality data for England and Wales during the period 1988 to 2025 in order to make these new mortality estimates.
The analysis found that those aged 65 years and over in each region of England and Wales experienced at least a 50 per cent increased mortality risk at temperatures exceeding 24C when compared with optimal temperatures.
In England, an estimated 40,063 deaths (0.21 per cent of all deaths) were associated with the hottest temperatures, and 138,944 (0.72 per cent of all deaths) with the coldest, between 1988 and 2025.
In Wales, an estimated 2,070 deaths (0.16 per cent of all deaths) were associated with the hottest temperatures, and 10,098 (0.79 per cent of all deaths) with the coldest.
Researchers said cold-related deaths were “substantially” higher in 2010 following a severe cold spell during the winter, and that heat-related deaths peaked during the extreme summer temperatures in 2022.
London had the highest percentages of total deaths that were associated with both the hottest and coldest temperatures, but the South East had the highest number of purely cold-related deaths.
Last year saw the warmest summer on record with four back-to-back heatwaves and a mean temperature of 16.12C across the UK.
The latest provisional Met Office data shows that in 2026, England has recorded a mean summer temperature of 18.19C so far meaning the remainder of August would need to be 1.41C below the summer average for England to equal its current warmest summer on record, also set in 2025.
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