Europe's summer of 2026 was its deadliest on record for heat-related deaths, according to a new modelling study. Researchers estimate that more than 50,000 people died across 854 urban areas in the EU, UK, Norway and Switzerland between June and August, with climate change responsible for roughly two-thirds of those excess deaths.
The toll far exceeds previous peaks: about 29,000 deaths in 2022 and 28,000 in 2003 across the same area. The continent, which is warming faster than any other, experienced a succession of heatwaves that pushed temperatures in Western Europe 2.9°C above the 1991-2020 average, with some days spiking as much as 12°C above normal.
“These numbers are a stark reminder that our hotter, more extreme summers are having an increasingly severe impact on public health,” said Dr Clair Barnes, co-author and extreme weather researcher at Imperial College London. “Behind these statistics are real people whose lives were lost and real families who grieve for them.”
How the death toll was calculated
The study, led by researchers at Imperial College London and the London School of Hygiene and Tropical Medicine, used temperature records and historical relationships between heat and mortality to estimate excess deaths. They factored in geography, socioeconomic conditions, health service access, and age-specific vulnerabilities. The modelling covered urban areas that are home to about 40% of the population of the 30 countries studied.
“The true burden of mortality due to heat is not directly observed or measured,” said co-author Dr Malcolm Mistry. “Heat is therefore often commonly referred to as a ‘silent killer’, with the death toll underreported in several regions globally.”
Nearly one-third of the estimated deaths occurred during an intense heatwave from 17 June to 1 July, when average temperatures were 5.3°C above normal. The researchers compared actual temperatures with a counterfactual scenario without human-induced warming, attributing 65% of heat-related deaths – around 32,000 – to climate change. In the early 2000s, that share was about 40%.
Dr Barnes stressed the dual need for adaptation and mitigation: “It is yet another reminder both of the imperative of rolling out targeted interventions to protect those who are most vulnerable to this increasingly extreme heat, and of the growing need to rapidly transition away from fossil fuels to slow the pace of change and limit future warming.”
Who was most at risk?
People aged 85 and over accounted for roughly half of the estimated deaths. But younger adults were not spared: there were about 800 excess deaths among those aged 20 to 44, and around 6,000 among people under 65. Vulnerable groups – the elderly, young children, those with pre-existing conditions, and people who cannot afford to cool their homes – were disproportionately affected.
Geographically, Southern Europe saw significantly more heat-related deaths than the north. This reflects higher temperatures, but also other factors. “For example, factors such as increased air pollution levels, limited green space infrastructure, accessibility to health systems and heat alerts,” explained co-author Dr Garyfallos Konstantinoudis of Imperial's Grantham Institute.
Which countries were hit hardest?
Italy suffered the highest estimated toll: 13,303 excess deaths. France followed with 7,268, Spain with 6,824, Germany with 6,340, and the UK with 4,354. Even traditionally cooler countries struggled, as infrastructure and habits were not designed for such heat.
“In the UK, the summer is historically the quietest time for our health service. This summer, however, saw demand and strain that was akin to a really bad winter virus season,” said Andrew Hartle, Professor of Practice of Anaesthesia at Imperial College Healthcare.
The findings underscore the urgency of preparing health systems for extreme heat events. Beyond cutting emissions, cities can invest in cooling infrastructure, early warning systems, and targeted support for the most vulnerable. As the continent faces more frequent and intense heatwaves, the human cost is becoming impossible to ignore.
