According to the assessment, an estimated 753 deaths were associated with the heat episode between May 24 and 27, while a further 2,124 deaths were linked to the June 21–28 heatwave.

Although the figures remain provisional, they are already approaching the annual record reported by UKHSA in 2022.

The June heatwave lasted for eight days and prompted the issuance of a Red Heat-Health Alert—only the second time the highest level of alert has been declared in England—highlighting the exceptional temperatures recorded, UKHSA said in a statement.

Both May and June also set new Met Office monthly temperature records for England. A temperature of 31.5°C was recorded at Kew Gardens on May 26, while 37.7°C was recorded at Lingwood, Norfolk, on June 26.

UKHSA said the findings underscore the importance of the Heat-Health Alert system, developed in partnership with the Met Office, which provides early warnings when high temperatures are expected to significantly affect public health and wellbeing.

The agency noted that heatwaves occurring earlier in the season can have a greater health impact because people, communities and essential services have had less time to adapt to rising temperatures.

To strengthen preparedness, UKHSA recently published the updated Adverse Weather and Health Plan for England 2026–2027, aimed at helping partners respond more effectively to extreme weather events.

Based on the interim assessment, UKHSA said 2026 is likely to record the highest number of heat-associated deaths on record, surpassing the 2,985 deaths reported in 2022, if further periods of extreme heat occur during the remainder of the summer.

Dr. Ross Thompson, Principal Environmental Public Health Scientist at UKHSA and author of the report, said: "These figures highlight the significant danger that very hot weather can pose to people's health. This is particularly true for those who are more vulnerable, including older adults and people with underlying medical conditions."

"While the figures are interim, they suggest that, if we experience more periods of hot weather this summer, we could see the highest number of heat-associated deaths on record," Thompson said.

"As the climate becomes warmer, we can expect periods of hot weather to become longer, more frequent and more extreme. That's why it's vital that individuals, communities and systems are prepared to deal with higher temperatures, and to ensure those most vulnerable to the heat are protected," he added.

Health and Social Care Secretary Yvette Cooper said: "The sweltering heat has had a serious impact this summer on people's health and on our NHS."

"For many years, we have been used to winter pressures in our NHS and the need to support those who are vulnerable in the coldest weather. But now we are seeing the summer heat have an increasingly serious impact on the health of thousands of people, and on the pressures facing our NHS too," Cooper said.

"My thoughts are with all those who have lost loved ones as a result of the long and intense heatwaves in recent months. And my heartfelt thanks go to the NHS staff, care workers and emergency responders who have worked tirelessly through these exceptionally busy and challenging months to protect and care for people affected by the heat," she added.

This year marks the hottest June recorded for Western Europe and the second warmest globally, according to the latest report from a climate tracking service released earlier this month.

“Heatwaves like this are what we expect to see in a changing climate,” said John Kennedy, head of climate information at World Meteorological Organization (WMO).

“In the 50 years since the historic heatwave in 1976, Europe as a whole has warmed by around two degrees. It’s the fastest warming continent, and extremes of temperature have increased too.”

The heat spikes are being driven by the highest sea surface temperatures on record for June, according to the monthly update from the continent’s Copernicus Climate Change Service.

Globally, the monthly average sea-surface temperature for the extra-polar ocean (60°S-60°N) was the highest for June, exceeding the previous record set in June 2024 by just 0.01ºC, partly reflecting the development of strong El Niño conditions in the equatorial Pacific, according to the service.

‘Silent killer’

Heat stress occurs when the body gains more heat than it can release, and extreme heat is often called the “silent killer”, remaining under-reported in many countries.

More than 200,000 heat-related deaths occurred in Europe over the past four years, according to the World Health Organization (WHO). Globally, WMO estimates there were approximately 489,000 heat-related deaths annually between 2000 and 2019.

Lachlan McIver, a health adviser at the WHO-WMO Climate and Health Joint Office, said most at risk are older adults, young children, pregnant women, outdoor workers and people unhoused or living with chronic illness, but heat stress can affect anyone when temperatures are extreme enough for long enough.