The Imperial College London analysis, published in peer-reviewed papers in *Nature Health*, estimates 50,391 heat-related deaths across 854 cities in 30 European countries from June through August 2026. Of those, 32,619 deaths are attributed to the extra heat caused by burning coal, oil and gas.

Study author Clair Barnes said the summer of 2026 is 'likely to have been the worst on record for heat-related mortality across much of Europe,' and the toll is the highest in 26 years, substantially above the previous deadliest summer of 2022, which killed 29,480 in the same cities.

The new detail beyond the headline toll is how much worse this summer was than anything in the 26-year record: researchers told NPR and the Telegraph Herald the death count is 71% higher than 2022's 29,480.

About a third of the deaths came in a single brutal stretch from June 17 to July 1, when temperatures ran 5.3°C above normal, according to co-author Garyfallos Konstantinoudis.

Some cities saw temperatures 12°C warmer than usual, and AccuWeather/CNN reports western Europe had its hottest summer on record, about 2.9°C above the 1991-2020 average.

The team modeled heat deaths by age group for each of the 854 cities using an established equation based on each city's localized optimal temperature for lowest mortality, then compared real 2026 deaths with computer simulations of a world without climate change.

Because heat deaths are underreported and often missing from death certificates, they also used statistical modeling for the base count — a method outside experts called state-of-the-art.

When checked against government figures, their estimate for the May and June British heat waves was 2,700 excess deaths against the UK health statistics agency's 2,800, Konstantinoudis said.

The share of heat deaths blamed on global warming has risen sharply, Barnes said — from about 45% in the early 2000s to 65% now.

AccuWeather/CNN put it slightly differently, reporting that fossil fuel pollution caused roughly 40% of heat deaths earlier this century compared with around two-thirds today.

Former U.S. National Center for Environmental Health director Dr. Howard Frumkin, who was not involved, said hotter summers plus more accurate attribution tools together yield 'increasingly high and increasingly accurate counts' of heat deaths.

More than half of those who died were 85 or older, but the heat also killed more than 800 people aged 20 to 44, and thousands under 65, a concern flagged by University of Warwick researcher Raquel Nunes in CNN's report.

Italy, France, Spain and Germany had the highest death tolls, and Rome recorded the highest heat-death total of any European capital from 2000 to 2025. Southern and western Europe were worst affected, though typically cooler northern regions including the UK also saw thousands of deaths.

The figures are underestimates: they exclude a deadly May heat wave and cover only cities holding about 40% of Europe's population.

The findings land just weeks before international leaders gather in Turkey for the annual UN climate talks, and days after a UN report warned the chance of limiting warming to 1.5°C has vanished, CNN noted.

Barnes said governments need faster, coordinated action, and 'until we kick the fossil fuel habit, we will continue to see increasingly hot and dangerous summers.'

Experts called for urgent investment in heat early-warning systems, equitable access to low-carbon cooling, and neighborhood buddy systems — while stressing adaptation is not enough.

'We can't just be mopping up the mess on the floor without thinking about turning the faucet off,' said Dr. Jonathan Patz of the University of Wisconsin-Madison.