Heatwave likely killed 263 people in London, study estimates

An extra 263 Londoners likely died in the recent heatwave, according to stark new estimates.

It has prompted warnings that British classrooms, homes and hospitals are ill-prepared to deal with increasing temperatures, as another heatwave kicks in today.

Last week temperatures reached up to 34.7C (94.5F) in the capital, which was under an amber health alert, warning of disruption to hospitals.

Meanwhile, Wimbledon players relied on ice packs to cope with the relentless, baking sun.

But away from the spotlight, 263 people are thought to have lost their lives between 23 June to 2 July, as the sun roasted flats, tarmac and care homes.

About 171 of these excess deaths were added by climate change, which made temperatures in the capital 3.95C higher than they would have been, according to experts.

It means climate change effectively tripled the number of people who died, the scientists from Imperial College London and London School of Hygiene & Tropical Medicine (LSHTM) concluded.

Just two or three extra degrees in a heatwave can be "the difference between life and death" for many people, said Dr Fredi Otto from Imperial College London.

"Climate change is an absolute game changer when it comes to extreme heat, but still very much under-recognised," she said.

The figures are not an actual count of the number of people who died, but a statistical analysis based on existing, peer-reviewed methods assessing heat deaths.

It chimes with previous official figures, which found 3,000 people died in the long hot summer of 2022.

Problem worse in Europe

While London was being baked by a "heat dome" over those 10 days, so was most of Europe, where hundreds more people are thought to have died.

Across 12 major cities, there were an estimated 2,300 heat deaths in the same period.

And two thirds of them (1,500) were also triggered by climate change tipping temperatures, and people's conditions, over the edge, the analysis said.

"Even without climate change, many places in Europe likely would have experienced a period of hot weather in the past couple of weeks," said Dr Ben Clarke from Imperial.

"But climate change has made it significantly hotter than it would have been, which in turn makes it a lot more dangerous."

How heat affects the body

Heat stresses the heart and kidneys as they try to cool the body down.

Those over 65 and with pre-existing medical conditions, like cardiovascular disease, and diabetes are at highest risk. But heat can kill younger people, with 296 people aged between 20 and 64 thought to have died in the last heatwave.

Young children - whose small bodies heat up faster - and pregnant women, who struggle to regulate body temperature, are also in danger from the heat, which has also been linked with risk premature births.

Poor or vulnerable people - who are less likely to access air conditioning or green spaces, and more likely to be forced to work in the scorching sun - are also in danger.

A construction worker in Italy and street sweeper in Barcelona are among those who died last week amid the heat.

What can be done?

The research has prompted fresh calls to adapt buildings and outdoor areas to protect Britons from temperatures their buildings were not designed to cope with.

"Alongside health, our education sector and schools are not fit to deal with heat," Dr Chloe Brimmicombe, who was not involved with the study, told Sky News.

"There has been no strategy from multiple governments to adapt the health, social and care sector buildings to heat, despite calls and research highlighting a huge need," she said, echoing repeated warnings from national advisers in April and in recent years.

Sky News has contacted the government's environment department, responsible for adapting the country to cope with heat, with a request for comment.

Air conditioning can reduce the danger indoors, but also risks adding to the problem and triggering blackouts. Climate experts call for other forms of cooling like shutters and trees.

(c) Sky News 2025: Heatwave likely killed 263 people in London, study estimates