Heat-Related Deaths Estimated in UK’s May and June Heatwaves
Experts estimate that more than 2,700 people may have died from heat-related causes during the UK’s exceptionally hot weather in May and June. This estimate comes from a collaborative team at Imperial College London, the Met Office, and the London School of Hygiene and Tropical Medicine, based on current knowledge of the health risks posed by extreme heat.
Most of these deaths are believed to have occurred during the June heatwave, which was the warmest June on record in England. Temperatures reached 37.7C (99.9F) at Lingwood, Norfolk, surpassing the previous record of 35.6C (96F) set in 1957. During this period, a rare red heat alert was issued for parts of England and Wales, warning even healthy individuals of a significant risk to life.
May also saw record-breaking temperatures, with a new UK high of 35.1C recorded at Kew Gardens on May 26. This was a notable increase from the previous high of 32.8C, which had stood since 1922 and was matched in 1944.
Both heatwaves were caused by a "heat dome," a stalled high-pressure system that trapped hot air over the region, according to experts. The heat dome’s intensity was exacerbated by human-induced climate change, which has warmed the planet by approximately 1.4C since pre-industrial times. Scientists estimate that climate change added between 3 and 4C to the maximum temperatures recorded in May and June.
Hot tropical nights contributed to the oppressive conditions, providing little relief from the heat. Many UK homes are not designed to withstand prolonged high temperatures, increasing vulnerability among residents.
Heat places significant physical strain on the body, especially when dehydration occurs. The heart must work harder and faster to cool the body, which can be dangerous. Vulnerable groups include babies, older adults, and individuals with pre-existing health conditions. Heat exposure can lead to increased incidents of heart attacks, strokes, and other potentially fatal emergencies.
Heat can affect anyone, including healthy individuals, and is often referred to as a "silent killer" because early symptoms can be easily missed. When heat is accompanied by high humidity, as it was in June, the body’s ability to cool itself through sweating is impaired.
Heatwaves and Future Risks
The study estimating deaths in May and June 2026 uses death records from previous years to model the potential impact of the heatwaves. It incorporates assumptions about the severity of heat effects on the population, so the actual outcomes may differ.
If by putting out these estimates we highlight to people how dangerous it is and they change their behaviour next time there's a heatwave and our estimates turn out to be high, I will be thrilled.
These are big numbers and we don't want to see this many people dying.
These remarks were made by Dr Clair Barnes, an expert in extreme weather and climate change at Imperial College London and a member of the research team.
Experts had anticipated that 2025 would be a particularly severe year for heat-related deaths, but the actual number of deaths was roughly half the predicted 3,039. The UK Health Security Agency (UKHSA) attributed this to heat health alerts and proactive measures taken by the NHS and care systems, which likely mitigated the impact.
Some researchers warn that if current trends continue, heat-related deaths in parts of northern Europe could approach or exceed cold-related deaths within a few decades. However, they emphasize that this outcome depends heavily on the pace of global climate emissions reductions and the effectiveness of adaptation strategies.
Heatwaves are expected to become more frequent, intense, and longer-lasting as greenhouse gas emissions continue to rise.
