More than 2,700 people may have died in England and Wales during searing heatwaves in May and June, according to new research that underscores how climate change is turning hot spells into a mounting public health crisis.

The analysis, carried out by scientists from Imperial College London, the UK Met Office and the London School of Hygiene and Tropical Medicine, combined detailed weather observations, climate modelling and historical data on excess deaths during hot periods. Their estimate suggests that hundreds of deaths occurred in late May, with the toll surging into the thousands during an intense spell of heat in late June.

Researchers concluded that about 42 percent of these deaths were likely driven by the additional heat made possible by human-induced global warming. In other words, without decades of greenhouse gas emissions, nearly half of the fatalities might not have occurred.

England recorded monthly temperature highs of 35.1°C in May and 37.7°C in June, levels scientists described as exceptional not only for their intensity but for how early in the year they arrived. Heatwaves of this magnitude have historically been rare in the UK, particularly before the peak summer months, but are becoming more frequent and more dangerous.

Public health experts warn that the official death toll is likely to rise. The UK Health Security Agency is preparing its own assessment based on death certificates and hospital data, which will provide a more granular picture of who was most affected, including older people, those with underlying health conditions and residents of poorly ventilated housing.

Researchers stress that their modelling is not a substitute for those official figures, but say it reveals the scale of the risk now facing the population. They estimate that climate change added around 3°C to 4°C to maximum daytime temperatures during the heatwaves, pushing conditions beyond thresholds that many vulnerable people can safely tolerate.

The findings add urgency to warnings from the Climate Change Committee, the government’s statutory adviser, which has repeatedly said the country is not prepared for escalating heat. The committee has urged ministers to set legal limits on workplace temperatures, retrofit homes to keep them cool and equip hospitals, care homes and schools to cope with more frequent extremes.

Scientists involved in the new study say the latest figures should be treated as a stark signal that heat is no longer a rare summer inconvenience, but a predictable and deadly consequence of a warming climate that demands rapid adaptation and deeper emissions cuts.