LONDON, UK – A severe heatwave gripping England and Wales is projected to cause nearly 600 excess deaths over a four-day period, according to a rapid analysis released by leading research institutions. The study, conducted by researchers at the London School of Hygiene & Tropical Medicine (LSHTM) and Imperial College London, estimates that approximately 570 people could die as a direct or indirect result of the high temperatures between Thursday, June 19, 2025, and Sunday, June 22, 2025.
This analysis represents the first real-time assessment of excess heat deaths in the UK for 2025. Utilizing decades of historical UK mortality and temperature data across a granular network of 34,753 areas, the researchers have developed a predictive model to forecast the potential impact of the current heatwave on public health.
Understanding the Predictive Model
The study’s methodology draws upon established links between high environmental temperatures and increased mortality rates. By analyzing long-term datasets, the researchers identified patterns and thresholds where heat significantly contributes to excess deaths, particularly among vulnerable populations. This sophisticated modelling allows for rapid projections during live heat events, providing critical information to public health authorities.
The forecast indicates a stark distribution of expected fatalities across the four-day period. On Thursday, June 19, 2025, an estimated 114 excess deaths were projected. This number is expected to rise sharply to 152 on Friday, June 20, 2025, peaking on Saturday, June 21, 2025, with an estimated 266 excess deaths as temperatures are forecast to exceed 32°C in some regions. The estimate for Sunday, June 22, 2025, shows a projected 37 excess deaths, as conditions potentially begin to ease.
Vulnerable Populations Most at Risk
The analysis underscores the disproportionate impact of heatwaves on older age groups. According to the study, older people above 65 are expected to account for the vast majority of these fatalities, comprising an estimated 488 of the approximately 570 excess deaths. Within this demographic, individuals aged 85 and over are particularly vulnerable, with the study predicting 314 of the estimated excess deaths occurring within this specific age bracket.
Heatwaves are often referred to by experts as “silent killers” because they can covertly exacerbate pre-existing health conditions, such as cardiovascular, respiratory, and renal diseases. The stress placed on the body’s thermoregulatory system by extreme heat can lead to organ failure or worsen chronic illnesses, often without immediate, obvious signs of heatstroke.
Public Health Response and Alerts
In response to the escalating heat risk, the UK Health Security Agency (UKHSA) had initially issued a yellow heat-health alert earlier in the week. Recognizing the increasing severity of the forecast temperatures and the potential health impacts, this was subsequently escalated to a more serious amber heat-health alert. The amber alert, signifying a higher level of public health concern, came into effect covering all of England by Thursday noon, June 19, 2025. The UKHSA warning explicitly cautioned the public about a potential “rise in deaths” directly attributable to the heat.
Health authorities and researchers alike are stressing the critical need for the public to adhere to health advice during this period of extreme heat. Recommendations typically include staying hydrated, seeking shade, avoiding strenuous activity during the hottest parts of the day, and keeping homes cool. A particular emphasis is placed on the importance of checking on vulnerable individuals, such as the elderly, young children, and those with chronic health conditions, who may be less able to regulate their body temperature or respond to the heat.
Long-Term Implications and Future Risks
Beyond the immediate crisis, the researchers warn that the UK faces a growing risk of large-scale heat-related mortality events in the future. Several factors contribute to this projected increase in risk. The UK has a significant and growing aging population, a demographic particularly susceptible to heat-related illnesses and death.
Furthermore, climate change projections indicate a substantial warming trend for the region. Scientists forecast a projected warming of 2°C by 2050, with the potential for temperatures to increase by as much as 3°C this century. Without robust and effective mitigation strategies to combat climate change and significant adaptation measures to help the population cope with higher temperatures, events like the current heatwave are expected to become more frequent and more intense, posing an increasing threat to public health and potentially leading to higher mortality figures in future years.
Experts argue that investments in cooling infrastructure, urban planning that considers heat resilience (such as increasing green spaces), and public awareness campaigns are crucial adaptation measures needed to protect populations from the health impacts of rising global temperatures.
The findings of this rapid study serve as a stark reminder of the immediate and future health challenges posed by extreme heat events in a warming climate and underscore the urgency of both short-term protective measures and long-term climate action.
