By Emeka Blast 
Researchers Project Nearly 600 Heat Deaths in UK Heatwave
By Emeka Blast – June 21, 2025
A scorching heatwave sweeping across England and Wales is projected to claim nearly 600 lives between Thursday, June 19, and Sunday, June 22, 2025, according to a rapid analysis by experts from the London School of Hygiene and Tropical Medicine (LSHTM) and Imperial College London. The study, released on Saturday, estimates 570 excess deaths due to the extreme heat, with temperatures peaking at 32°C in London and the South East. The surge in mortality, driven by human-caused climate change, underscores the growing public health threat posed by heatwaves in the UK.
Heatwave’s Deadly Toll
The heatwave, which has gripped the region since Thursday, is expected to result in 570 premature deaths over four days, with the highest toll of 266 deaths projected for Saturday, June 21, when temperatures are at their most intense. London is anticipated to bear the brunt, with 129 excess deaths, followed by the West Midlands, according to the researchers’ analysis. The study, based on decades of UK mortality data and high-resolution weather forecasts from the Copernicus climate change service, highlights the lethal impact of temperatures in the high 20s to low 30s, particularly for vulnerable groups.
Older adults, especially those over 65, are the hardest hit, accounting for 488 of the estimated deaths, with 314 among those aged 85 and over. However, the heatwave poses risks across all ages, with 82 deaths projected for those under 65. “Exposure to temperatures in the high 20s or low 30s may not seem dangerous, but they can be fatal, particularly for people aged over 65, infants, pregnant people, and those with pre-existing health conditions,” said Dr. Malcolm Mistry, assistant professor at LSHTM.
The analysis notes that the early summer timing of the heatwave, before populations are acclimatized to high temperatures, may lead to an underestimation of deaths. Incidents such as dozens requiring treatment for heat-related illnesses at Royal Ascot on Thursday underscore the immediate health impacts.
Climate Change as a Driver
The heatwave’s severity is amplified by climate change, with the World Weather Attribution (WWA) group reporting on Friday, June 20, that it is 100 times more likely and 2-4°C hotter due to fossil fuel emissions. “A large number of the excess deaths wouldn’t have likely happened without climate change,” said Professor Antonio Gasparrini of LSHTM, emphasizing that “every fraction of a degree of warming will cause more hospital admissions and heat deaths, putting more strain on the NHS.”
The UK Health Security Agency (UKHSA) issued an amber heat-health alert covering all of England, warning of “a rise in deaths” and “significant impacts” on health and social care services. The alert, in effect until 9 a.m. Monday, June 23, advises avoiding sun exposure between 11 a.m. and 3 p.m., staying hydrated, and checking on vulnerable individuals, particularly older adults living alone.
Dr. Lorna Powell, an NHS urgent care doctor in east London, reported a rise in heat-related illnesses, noting, “Heat exhaustion can quickly trigger more serious illnesses as dehydration sets in and the cardiovascular system becomes overwhelmed.” Posts on X reflect public concern, with users like @aliya_Hshah highlighting the 600-death estimate and urging action to address climate-driven heat risks.
Rising Threat and Future Risks
The current heatwave follows a troubling trend, with the UKHSA reporting over 10,000 premature deaths during summer heatwaves between 2020 and 2024. A 2022 heatwave, when temperatures hit 40°C, caused nearly 1,100 deaths, aligning with the current projections. A recent UK Climate Change Committee report warns that heat-related deaths could exceed 10,000 annually by 2050 if global warming reaches 2°C, a scenario UN scientists say the world has three years to avert by limiting warming to 1.5°C.
Dr. Garyfallos Konstantinoudis of Imperial College London called heatwaves “silent killers,” as deaths often involve pre-existing conditions exacerbated by heat, rarely listing heat as the direct cause. “This real-time analysis reveals the hidden toll of heatwaves, and we want it to help raise the alarm,” he said, urging adherence to heat-health advice.
Urban areas, particularly inner-city homes, face heightened risks due to poor ventilation and overheating, with 80% of UK homes reported to overheat in summer. High ozone air pollution in London on Saturday further endangers those with lung conditions, prompting warnings to limit exercise.
Mitigation and Adaptation Needs
Experts stress the urgency of mitigation and adaptive measures to address the escalating threat. “Unless effective measures are put in place in the coming years, the risk of large heat-related death events is set to increase in the UK,” warned Dr. Mistry, citing the aging population and projected warming of 2°C by 2050, potentially reaching 3°C this century.
The government’s climate preparedness was criticized as “inadequate, piecemeal, and disjointed” by official advisers in April 2025, highlighting gaps in protecting vulnerable populations. Calls to stop burning coal, oil, and gas are growing, with researchers arguing that stabilizing the climate is critical to preventing further preventable deaths.
Public Response and Recommendations
Public sentiment on X reflects alarm, with posts like @LSHTM’s citing the 600-death estimate and urging action, while skeptics like @Raymond82310289 question the severity, claiming, “It’s not even that hot.” Health officials counter that temperatures in the low 30s can be deadly, particularly for those with heart, respiratory, or diabetes issues, as heat stresses already compromised systems.
The UKHSA recommends staying out of the sun during peak hours, drinking plenty of water, and ensuring older adults and vulnerable neighbors are supported. As the heatwave continues, the NHS faces increased pressure, with hospitals reporting rising cases of heat exhaustion and related illnesses.
Looking Ahead
As England and Wales brace for the heatwave’s peak on Saturday, the projected 570 deaths serve as a stark reminder of climate change’s human cost. With heatwaves becoming more frequent and intense, experts warn that without significant action, the UK faces a future of escalating health crises. The current crisis, coupled with projections of 10,000 annual heat deaths by 2050, underscores the need for robust climate policies and public health measures to protect the most vulnerable.
Summary Table: Heatwave Impact (June 19-22, 2025)
| Aspect | Details |
|---|---|
| Estimated Deaths | 570 total (114 Thu, 152 Fri, 266 Sat, 37 Sun) |
| Peak Day | Saturday, June 21 (266 deaths) |
| Most Affected Area | London (129 deaths) |
| Vulnerable Group | Over 65 (488 deaths, 314 aged 85+) |
| Climate Change Impact | Heatwave 100x more likely, 2-4°C hotter |
| Health Alert | Amber heat-health alert until 9 a.m. Monday, June 23 |
| Future Risk | 10,000+ annual deaths by 2050 if warming reaches 2°C |
