More than 40,000 people died in England due to extreme heat between 1988 and 2025, new figures have revealed.

Those deaths were especially concentrated in London, where 7,675 extra people died on the hottest days over the last four decades.

These figures, provided by the Office for National Statistics (ONS), do not include this year's summer, which is likely to see the highest ever number of heat–related deaths.

In what experts are calling a 'shocking national scandal', this presents the very real possibility that summer heat deaths will soon outstrip deaths on the coldest days.

In the past, it has been argued that climate change is an acceptable risk for the UK because milder winters would reduce cold deaths faster than heat deaths increased.

However, as the UK Health Security Agency estimates that 2,877 died in this year's May and June heatwaves alone, that suggestion looks far less certain.

Bob Ward, of the Grantham Research Institute on Climate Change and the Environment, told the Daily Mail: 'These figures show that summer heat is now killing almost as many people as winter cold each year in England and Wales.

'This is a shocking national scandal, and if we had this number of deaths from flooding there would be widespread and justifiable outrage.'

In 2025 alone – the most recent year for which there is data – 2,805 people died on the hottest days in England and Wales who would have survived in cooler weather.

That is greater than the 2,244 cold–related deaths that occurred on the coldest days that year.

The ONS calculates 'climate–related mortality' by measuring the number of people who died on the hottest and coldest 2.5 per cent of days who would have survived in normal weather.

Historically, cold–related excess deaths in the winter have massively outweighed those deaths that occurred on the hottest days.

In England between 1988 and 2025, ONS data shows that there were almost 139,000 deaths on the coldest days – more than triple the number of heat–related deaths.

Likewise, in Wales, more than 2,000 excess deaths were recorded on the hottest days during the same period, compared with 10,000 on the coldest.

Extreme heat places the body under massive stress and is especially deadly for the elderly and young children.

High temperatures increase the risk of heart attacks and strokes, exacerbate existing conditions such as asthma and kidney ailments, and wear down the body's defences with successive nights of poor sleep.

Dr Clair Barnes, Climate Scientist at Imperial College London, says: 'Both extreme cold and extreme heat can have severe consequences on health.

'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.'

In fact, in some areas, heat deaths are already overtaking cold deaths as the leading source of climate–related mortality, in a reversal of decades–long trends.

In 2025, more people died due to extreme heat than extreme cold in every part of England and Wales except for the northwest and southeast of England.

That year, there were a total of 2,805 heat–related deaths in England and Wales, and just 2,244 deaths attributed to cold.

That reversal is partly due to fewer deaths occurring in the winter, but has also been driven by a significant increase in heat–related excess mortality.

Dr Barnes adds: '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.'

Now, researchers expect that this summer's heatwaves will propel an even greater spike in heat–related deaths.

The UKHSA estimates that there were 753 heat–related deaths in May alone, and a further 2,124 during the June heatwave.

That is double the national figures for the entirety of summer in 2025, with UK A&E departments experiencing their busiest periods ever, with heat cited as the primary reason.

While naturally forming weather patterns are responsible for the heatwave's formation, scientists say that climate change made the event significantly more deadly.

Climate change not only makes extreme weather events more likely, but ensures that they occur against hotter background conditions.

According to an analysis conducted by scientists at Imperial College London, 42 per cent of the 2,700 people killed by heat–related causes between May and June died as a direct result of human–caused warming.

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 we continue to heat our 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.'