Heatwave likely killed 263 people in London, scientists estimate

Experts say the intense heat was a result of climate change

From June the 23rd until the 2nd of July 2025, temperatures right across Europe soared as a “heat dome” trapped hot dry air on the continent, leading to highs of 34C in London’s St James' Park. 

According to a new report released by Imperial College London and the London School of Hygiene and Tropical Medicine (LSHTM), these unexpected temperature rises — which saw the capital city reach levels at least 4C higher than they should’ve been — were caused by climate change. 

In London, estimates say 171 of the deaths were a direct result of climate change, as global warming caused heat-related deaths in twelve European cities to triple.

Climate change is the long-term warming of global temperatures caused in main by human activities like the burning of fossil fuels.

Greenhouse gases, released as a by-product of those activities, trap heat in the earth's atmosphere rather than letting it escape.

Dr Ben Clarke, researcher at the Centre for Environmental Policy at Imperial College London, said: “Heatwaves don’t leave a trail of destruction like wildfires or storms.

“Their impacts are mostly invisible, but quietly devastating - a change of just 2 or 3C can mean the difference between life and death for thousands of people.

“Our study shows how dangerous climate change already is with just 1.3C of warming.

“However, we could reach 3C this century, unless countries speed up the transition from fossil fuels to renewable energy.

“That would bring fiercer heatwaves to Europe, causing more deaths and placing greater pressure on health systems.”

This shocking report comes as the UK Health Security Agency (UKHSA) issued another yellow warning for heat, with another heatwave likely to take place over the next seven days.