More than 40,000 people have died in England due to extreme heat between 1988 and 2025, according to new figures released by the Office for National Statistics (ONS). This toll, particularly concentrated in London with 7,675 excess deaths on the hottest days over the last four decades, does not yet include the current year's summer, which is anticipated to set a new record for heat-related fatalities.
Experts are describing the situation as a "shocking national scandal," highlighting the growing possibility that heat-related deaths during summer could soon surpass those caused by cold weather in winter. Historically, excess deaths during colder months significantly outweighed those from heat. Between 1988 and 2025, nearly 139,000 deaths occurred on the coldest days in England and Wales, more than triple the number of heat-related deaths during the same period. Similarly, Wales recorded over 2,000 excess deaths on the hottest days compared to 10,000 on the coldest.
However, this trend is shifting as summer heatwaves become more frequent and intense. In 2025, the most recent year with complete data, 2,805 people died on the hottest days in England and Wales, exceeding the 2,244 cold-related deaths on the coldest days that year. In fact, heat deaths surpassed cold deaths in almost every region of England and Wales in 2025, with the exceptions of the northwest and southeast.
Dr. Clair Barnes, a Climate Scientist at Imperial College London, noted that while extreme cold has historically presented the highest health burden, this is changing. "We now face the very real prospect of heat deaths overtaking those that occur on the coldest days," she stated. This reversal is attributed to both a decrease in winter deaths and a substantial rise in heat-related excess mortality.
Extreme heat places significant stress on the body, posing particular risks to the elderly and young children. High temperatures can trigger heart attacks and strokes, worsen existing conditions like asthma and kidney ailments, and weaken the body's defenses through prolonged periods of sleep deprivation.
This year's heatwaves are expected to cause an even greater spike in heat-related deaths. The UK Health Security Agency (UKHSA) estimated 753 heat-related deaths in May and an additional 2,124 during the June heatwave. These figures are double the total for the entire summer of 2025, leading to record-breaking demand on UK A&E departments.
Scientists attribute the increased deadliness of these events to human-caused climate change. While natural weather patterns initiate heatwaves, climate change exacerbates their intensity and duration by raising background temperatures. An analysis by Imperial College London found that 42% of heat-related deaths between May and June were a direct result of human-caused warming.
Gareth Redmond-King, Head of the International Programme at the Energy and Climate Intelligence Unit, warned that without swift action to reduce emissions, current hot summers will become the norm. "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 stated.
The Paris Agreement, signed in 2015, aims to limit global warming to well below 2°C above pre-industrial levels, with an ambition to restrict it to 1.5°C. Experts emphasize the increasing importance of this 1.5°C goal, as previous research suggests that exceeding it could lead to significant increases in drier conditions globally. The agreement outlines four main goals for emissions reduction, including peaking global emissions as soon as possible and undertaking rapid reductions thereafter, guided by the latest scientific evidence.
Excess heat deaths have been particularly concentrated in London.
