UK heatwave deaths surpassed 2,700 across England and Wales during two unusually early hot spells in May and June, according to new research published on Monday.

Scientists estimated that 550 heat-related deaths occurred between May 21 and 29, followed by nearly 2,200 between June 18 and 28. The figures cover two record-breaking heatwaves in a year when England reached 35.1C in May and 37.7C in June. For a country still debating whether ceiling fans count as infrastructure, those numbers are not small.

How researchers estimated the death toll

Researchers at Imperial College London, the Met Office and the London School of Hygiene and Tropical Medicine carried out the study.

They combined weather observations, climate models and existing research on excess deaths during extreme heat. Excess deaths means the number of deaths above what would normally be expected for that time of year, rather than a count based on heat being listed on death certificates.

That distinction matters. Heat often worsens existing health conditions, particularly heart and respiratory problems, so its role can be undercounted in official records. The study estimates deaths linked to the heat, not a final certified tally.

The UK Health Security Agency plans to publish its own official estimate of heat-related deaths in the coming weeks, using death records from the recent heatwaves.

Why the May and June heatwaves stood out

The United Kingdom and much of Europe have already experienced two record heatwaves this year. In England, temperatures hit 35.1C in May, or 95.2F, and 37.7C in June, or 99.9F.

Mark McCarthy, science manager at the Met Office’s climate attribution team, said the timing made the heat especially notable.

“They were extreme heatwaves for the UK, and for all parts of Western Europe, and they’re particularly exceptional for the timing and how early in the year they occurred,” he said.

Early-season heat can be more dangerous because people, buildings and public services have had less time to adapt. It can also arrive before households, care homes and hospitals have shifted into summer preparation mode. The weather, with admirable indifference, does not wait for administrative readiness.

What scientists say climate change added

Researchers said climate change is making heatwaves more frequent and more intense. In this case, they estimated that maximum daytime temperatures were up to 4C higher than they would have been without global warming.

That figure is an attribution estimate, based on climate modelling rather than a direct thermometer reading from an alternate Earth. Still, it is consistent with the wider scientific picture: as average temperatures rise, the hottest events tend to become hotter, and dangerous heat becomes more common.

Lea Berrang Ford, of the UK Health Security Agency’s Centre for Climate and Health Security, said the study would “help illustrate the scale of risk associated with extreme heat and the growing threat climate change poses to our wellbeing”.

The findings add pressure to a policy debate that has not exactly been short of warnings.

Why the UK is being warned it is not prepared

The Climate Change Committee, which advises the British government on climate policy, warned last year that the UK was “not ready” for the consequences of climate change.

In a report published in May, the committee estimated that 92 percent of British homes could be too hot by 2050. That is not just a comfort issue. Overheated homes can be dangerous for older people, young children, people with disabilities and those with chronic illness.

The committee said the government should consider measures including:

  • Setting maximum temperature limits in workplaces
  • Investing in air conditioning for public buildings such as hospitals and schools
  • Preparing public services for more frequent periods of extreme heat
  • Improving homes so they are better able to stay cool during hot weather

The challenge is partly architectural. Much of the UK housing stock was built to retain heat, which is useful for winter and rather less charming when bedrooms turn into storage heaters.

Europe’s wider heat death toll is also rising

The UK estimates arrived alongside data showing more than 10,000 excess deaths across Europe during late-June heatwaves in the continent’s west.

EuroMOMO, a monitoring network supported by the European Centre for Disease Prevention and Control and the World Health Organization, said most of those deaths were among people aged 65 and over. About 9,000 excess deaths were reported in that age group.

Scientists pooled national mortality statistics from 27 European countries and found 10,650 excess deaths between June 22 and 28. They said that, in the absence of other major factors such as COVID-19 outbreaks, the heatwave most likely contributed to the spike.

The pattern is familiar and grimly practical: heat risk rises sharply with age, illness, poor housing and limited access to cooling. The new UK study puts a number on that risk for two early-season heatwaves, while the wider European figures show the pressure is not confined to one country.

The official UK count may refine the total. It is unlikely to make the underlying problem look smaller.