A severe heatwave that affected Europe from 22 to 28 June 2026 may have caused between 17,000 and 25,000 deaths, according to an early modelling estimate by Christopher Callahan of Indiana University. The central estimate is about 20,390 deaths, including more than 5000 in France, around 4500 in Germany, more than 3000 in Spain and 862 in the UK.
The estimate is based on earlier research linking temperature data with excess mortality across Europe. Callahan’s team used historical relationships between heat and death rates to estimate how many additional deaths may have occurred during the June event. He cautioned that the numbers are preliminary, but said they indicate the scale of risk posed by extreme heat.
Official counts so far are much lower. The World Health Organization has referred to more than 1300 reported excess deaths, including figures from France. Public Health France reported around 1000 more deaths than expected between 24 and 26 June, but noted that its reporting system is incomplete, covering only part of hospital, care-home and at-home deaths. Final mortality data may take months to confirm, partly because heat is often not listed directly on death certificates.
Some researchers said the estimate should be treated carefully. Dann Mitchell of the University of Bristol said 20,000 deaths in one week would be a very large figure and would require close examination of the modelling. Marcin Walkowiak of Poznań University of Medical Sciences said the use of 2015-2019 data may overstate current vulnerability, since adaptation measures such as air conditioning may have reduced risk. His rough estimate is closer to 15,000 deaths.
Other uncertainties remain. Early-summer heatwaves can be more deadly than later ones, and some heat-related health effects may occur after the initial event. Researchers broadly agree that improved planning in health, housing, social care and transport will be important as extreme heat becomes more frequent.