An estimated 50,391 people died from extreme summer heat across 854 cities in 30 European countries between June and August 2026, according to two peer-reviewed studies published in Nature Health.
Researchers at Imperial College London and the London School of Hygiene & Tropical Medicine linked roughly two-thirds of those deaths to human-caused climate change, driven mainly by fossil fuel emissions.
The figure makes summer 2026 the deadliest on record for heat-related mortality in the cities studied, the researchers said.
How researchers counted the deaths
The urban areas covered represent about 40% of the population in the countries examined, so the findings cannot establish a full death toll for Europe's towns and rural communities.
The team compared observed temperatures with estimates of what temperatures would have been without human-caused climate change.
Using established relationships between heat exposure and mortality, the scientists modeled likely deaths rather than relying on official death certificates.
The studies estimated that more than 32,600 deaths were attributable to climate change.
That contribution has risen from approximately 40% at the start of the century to around 65% in 2026, underscoring the growing influence of human-caused warming.
Clair Barnes, a researcher in extreme weather and climate change at Imperial College London and lead author of both studies, said the results reflected the substantial impact of rising temperatures on mortality.
"Even in a preindustrial climate, for some of these heat waves, we would have expected to see high mortality.
But that mortality has been pushed substantially higher by the human-caused warming, primarily from the burning of fossil fuels," Barnes said.
Hottest summer on record in western Europe
Western Europe experienced its hottest summer on record, with average temperatures 2.9 degrees Celsius above the 1991–2020 average.
In some countries, individual days were more than 12 degrees Celsius hotter than the seasonal norm, while persistent heat affected large parts of the continent from late May through August.
Estimated death rates were highest in Malta, Italy and Hungary.
Italy, France, Spain, Germany and the United Kingdom recorded the largest absolute numbers of deaths, while Naples emerged as the hardest-hit city in the analysis.
In Naples, age-standardized estimates indicated 815 heat-related deaths per million people.
Mario Guarino, an emergency physician at Ospedale CTO in northern Naples, reported a 15% increase in emergency room visits during the hottest weeks.
Guarino said extreme temperatures frequently compounded existing medical and social vulnerabilities, particularly among older people living alone and households unable to afford cooling.
He described cases involving a terminally ill cancer patient living in a hot attic because the family could not arrange air-conditioning installation, and an older man with dementia found injured after his caregiver left to visit her son, who had been called to war.
"The real epidemic these days is loneliness," Guarino said.
He added that many older people spend the summer without adequate support and cannot afford air conditioning or avoid using it because of electricity costs.
The researchers also identified poverty and social isolation as factors that can increase the danger posed by prolonged heat.
People aged 85 and older accounted for almost half of the estimated deaths, according to the analysis.
More than 800 people between ages 20 and 44 also died from heat-related causes, showing that the risks extended beyond the oldest age groups.
Official mortality statistics may underestimate the effects of extreme heat because death certificates do not always identify high temperatures as a contributing factor.
Heat can worsen cardiovascular and respiratory conditions, pushing people with existing illnesses beyond their physiological limits without being recorded as direct heatstroke fatalities.
David García-García, a researcher with the mortality monitoring system at the Carlos III Health Institute in Madrid who was not involved in the studies, described the analysis as a useful way to compare heat-related mortality across countries.
He cautioned that the estimates were based on temperature observations and epidemiological models rather than actual death records from summer 2026.
The findings come as Europe continues to warm at approximately twice the global average, according to the source reports.
Although cold temperatures currently cause more deaths overall than heat in Europe, scientists expect rising temperatures to increase heat-related fatalities faster than deaths from cold decline.
Researchers and health experts have called for faster reductions in fossil fuel emissions alongside measures to protect people during heat waves.
Recommended measures include strengthening health services, expanding urban green spaces, improving access to cooling, encouraging hydration and shade, and ensuring that vulnerable neighbors and relatives receive regular check-ins.
