Latest data published by the UK Health Security Agency (UKHSA) shows that there were an estimated 1,504 heat-associated deaths during the summer of 2025 across five heat episodes that met the UKHSA definition.
Summer 2025 was the warmest UK summer on record, with a mean temperature of 16.1°C, but the number of heat-associated deaths observed was significantly lower than expected. Based on recent historical associations between temperature and mortality, modelled estimates predicted 3,039 heat-associated deaths for England during the 2025 heat episodes. This means 1,535 fewer deaths were observed than anticipated and this pattern was consistent across all five heat episodes.
There are likely to be several factors contributing to this reduction, and it is difficult to ascertain causality, but system-wide response to heat, including national and local implementation of the Adverse Weather and Health Plan and heat alerts, as well as actions taken across the health, social care, and emergency response sectors may have contributed to harm-reduction during these periods.
Further evaluation is needed to understand the extent of this impact and other potential contributory factors, including whether warmer conditions in late spring may have encouraged early protective behaviours in the population ahead of the main alerting periods.
This estimate of 1,504 heat-associated deaths is higher than the 1,311 reported during the summer of 2024, which was the coolest UK summer since 2015, but considerably lower than the 2,295 reported in 2023 and the 2,985 estimated in 2022, the summer that saw the UK’s highest ever recorded temperature of 40.3°C.
As in previous years, the highest heat-associated mortality rates were observed in older age groups, with those aged 85 years and over experiencing the highest rate of 364 heat-associated deaths per million population, followed by those aged 75 to 84 years at 116 per million population. There was no statistically significant heat-associated mortality in younger age groups.
Dr Agostinho Sousa, Head of Extreme Events and Health Protection at UKHSA, said:
As shown in our latest assessment, the relationship between periods of hot weather and increased mortality remains clear. Even as we adapt to a changing climate, older adults and those with underlying health conditions continue to face the greatest risks.
The fact that observed heat-associated deaths were significantly lower than modelled estimates across all five heat episodes suggests that the actions taken across the health and care system may be helping to reduce harm.
However, with summer 2025 being the warmest on record, these findings reinforce the need for sustained vigilance. As periods of heat become more intense, longer and more frequent, coordinated preparation and response remain essential to protect the most vulnerable in our society.
Heat-associated deaths were predominantly observed in southern, central and eastern regions of England. These figures are consistent with where the heat was felt over the season. Unlike in several previous summers, there was no statistically significant heat-associated mortality detected in the North East, North West or Yorkshire and The Humber.
Significant heat-associated mortality was observed in care homes, hospitals, and people’s own homes, with care homes seeing the largest increase compared with baseline mortality.
Analysis by cause of death shows that circulatory diseases remained the most common underlying cause for heat-associated deaths. Cancer was the second most common cause, a finding that has emerged for the first time and will require further investigation. Significant heat-associated deaths were also observed for dementia and Alzheimer’s disease.
UKHSA has published the updated Adverse Weather and Health Plan for England for 2026 to 2027, which supports local and national organisations to prepare for and respond to adverse weather events, including heatwaves.
