UK heatwave could cause nearly 600 deaths, experts warn

21 June 2025, 00:00 | Updated: 21 June 2025, 23:01

By Rose Morelli

@sadlittlejourno

Experts have predicted that 600 people in England and Wales will die as a result of the heatwave - as Saturday was officially declared the hottest day of the year so far.

Researchers at the London School of Hygiene and Tropical Medicine (LSHTM) and Imperial College London used decades worth of data to predict excess mortality in relation to temperature, and announced around 570 people will die from excess heat over the four day hot spell between Thursday and Sunday.

The excess deaths are expected to peak at around 266 on Saturday, when the heat will be at its most intense.

The Met Office has said temperatures will peak at 32C in the South East on Saturday afternoon, between the hours of 2pm and 7pm.

London is predicted to have the greatest number of excess deaths during this period, with the toll expected to reach 129.

Read More: Met Office warns of 'significant' health risk as UK bakes on hottest day of the year

Read More: Searing heat this week made ‘100 times more likely’ by climate change, say scientists

The study estimated 114 of the excess deaths would have occurred on Thursday, 152 on Friday, and the remaining 37 on Sunday, when temperatures will fall back to the mid-20s.

Friday was the warmest day of the year so far, reaching temperatures of 30.8C - but that record is set to be smashed on Saturday.

The researchers have said this study highlights how extreme heat poses a growing threat to public health in the UK.

Heatwaves can pose serious risks to those with already compromised or fragile health, and the UK Health Security Agency issued an amber heat-health alert covering all of England.

The Met Office and the World Weather Attribution (WWA) have also issued similar warnings.

The Met Office warned of a ‘significant’ risk to health on Friday, citing worries about the impact on social and healthcare resources across the country.

Similarly, the WWA published a group study on Friday that found the heatwave had been made 100 times more likely and 2-4C hotter by climate change - meaning more frequent and intense heatwaves could become the norm.

It’s also been reported that dozens of people required treatment for heat-related illness at the Royal Ascot on Thursday.

People above 65 are expected to be affected most by the hot weather, taking up 488 of the projected excess deaths.

But the study has also made note of how heat can still be life-threatening for all ages, with 82 of the deaths projected for those under the age of 65.

The study reached its conclusions by collating decades’ worth of data and research into the relationship between heat and daily death count, regardless of cause.

They then combined these with high-resolution weather projections from the Copernicus climate change service.

The researchers did note that this number could be an under-estimation however, as they didn’t take into account the fact the heatwave happened early in the season before people had a chance to acclimatise to hot weather.

More than 10,000 people died prematurely in summer heatwaves between 2020 and 2024, according to the UK Health Security Agency (UKHSA).