More than 40,000 people died from extreme heat in England between 1988 and 2025, according to new figures from the Office for National Statistics.
The data reveals that heat-related deaths in England and Wales are now overtaking fatalities caused by cold weather, a shift experts have described as a "national scandal."
In 2025, the most recent year with available data, 2,805 people died on the hottest days in England and Wales who would have survived in cooler weather. This surpassed the 2,244 cold-related deaths recorded on the coldest days that year.
London saw the highest concentration of heat fatalities, with 7,675 extra deaths on the hottest days over the past four decades.
Changing climate trends
Historically, winter weather has killed far more people than summer heat. Between 1988 and 2025, almost 139,000 people died on the coldest days in England, which is more than triple the number of heat-related deaths.
In Wales over the same period, more than 2,000 excess deaths occurred on the hottest days, compared with 10,000 on the coldest.
The ONS measures climate-related mortality by calculating the number of people who died on the hottest and coldest 2.5 percent of days who would have survived in normal weather.
But the trend reversed in 2025, when more people died from extreme heat than extreme cold in every part of England and Wales except the northwest and southeast of England. The regional breakdown for climate-related mortality in 2025 showed:
- Wales: 133 heat deaths, 95 cold deaths
- North East: 135 heat deaths, 119 cold deaths
- North West: 224 heat deaths, 315 cold deaths
- Yorkshire and The Humber: 238 heat deaths, 204 cold deaths
- East Midlands: 314 heat deaths, 173 cold deaths
- West Midlands: 409 heat deaths, 243 cold deaths
- East of England: 346 heat deaths, 294 cold deaths
- London: 412 heat deaths, 247 cold deaths
- South East: 360 heat deaths, 372 cold deaths
- South West: 234 heat deaths, 182 cold deaths
A growing national threat
Extreme heat puts the body under massive stress and is particularly deadly for the elderly and young children. It increases the risk of heart attacks and strokes, worsens conditions such as asthma and kidney ailments, and wears down the body's defences through successive nights of poor sleep.
"These figures show that summer heat is now killing almost as many people as winter cold each year in England and Wales," Bob Ward of the Grantham Research Institute on Climate Change and the Environment told the Daily Mail.
"This is a shocking national scandal, and if we had this number of deaths from flooding there would be widespread and justifiable outrage."
It was previously argued that climate change was an acceptable risk for the UK because milder winters would reduce cold deaths faster than heat deaths increased, but experts say this suggestion now looks far less certain.
Surging summer fatalities
The ONS figures do not include this year's summer, which researchers expect will see the highest ever number of heat-related deaths.
The UK Health Security Agency estimates that 2,877 people died in the May and June heatwaves alone. This included 753 heat-related deaths in May and a further 2,124 during the June heatwave.
This is double the national figures for the entirety of summer in 2025. Heat was cited as the primary reason for UK A&E departments experiencing their busiest periods ever.
The impact of human-caused warming
Scientists say that while naturally forming weather patterns caused this summer's heatwave, climate change made the event significantly more deadly by ensuring it occurred against hotter background conditions.
An analysis by scientists at Imperial College London found that 42 percent of the 2,700 people killed by heat-related causes between May and June died as a direct result of human-caused warming.
"Both extreme cold and extreme heat can have severe consequences on health," said Dr Clair Barnes, a climate scientist at Imperial College London.
"This data demonstrates that while extreme cold historically had the highest health burden in England and Wales, that is shifting and we now face the very real prospect of heat deaths overtaking those that occur on the coldest days."
Dr Barnes added: "Fewer deaths in winter is clearly a good thing, but as this summer has made abundantly clear, the risk from extreme heat is a fast-growing problem that will only worsen without further action to reduce emissions and provide cooling, especially for vulnerable groups."
Calls for urgent action
Gareth Redmond-King, head of international programme at the Energy and Climate Intelligence Unit, said extreme heat is a growing threat to lives in the UK as people continue to heat the planet by burning oil and gas and adding greenhouse gases to the atmosphere.
"If we don't speed our way to net zero emissions, then this hot and dangerous summer will be one of the coolest of the rest of our lives, and the extreme heat will kill more and more people, particularly the most vulnerable," he said.
The Paris Agreement
The Paris Agreement, signed in 2015, is an international treaty aimed at controlling climate change. According to previous research, 25 percent of the world could see a significant increase in drier conditions, making its goals increasingly important.
The agreement has four main goals for reducing emissions:
- A long-term goal of keeping the increase in global average temperature to well below 2°C above pre-industrial levels.
- To aim to limit the increase to 1.5°C, since this would significantly reduce the risks and impacts of climate change.
- For global emissions to peak as soon as possible, recognising that this will take longer for developing countries.
- To undertake rapid reductions thereafter in accordance with the best available science.
