An estimated 1,257 deaths in Switzerland between May and August 2026 were attributable to heat, according to a preliminary report by the Swiss Tropical and Public Health Institute, commissioned by the Federal Office of Public Health.
The summer was Switzerland’s hottest since records began, surpassing even 2003. The estimated death toll was substantially higher than in previous years, accounting for 5.5% of all deaths during the period, or 14 deaths per 100,000 people. About 85% of those deaths were among people aged 75 or older.
The figures are statistical estimates rather than a count of deaths individually confirmed as caused by heat. The estimated toll has a 95% confidence interval of 1,053 to 1,479.
About seven in ten heat-related deaths were attributed to hot or very hot days. An estimated 485 were associated with daily mean temperatures of at least 25°C but below 27°C, and 400 with temperatures of 27°C or more. The remaining deaths were associated with more moderate heat.
Air conditioning may help protect older people. A study of 615 nursing homes in Ontario, Canada, published in JAMA Internal Medicine, found that extreme heat was associated with an 11% rise in the odds of death in homes without air conditioning, compared with 3% in those with it. The findings suggest that cooling could reduce deaths, though they are not directly applicable to Switzerland.
Allowing for statistical uncertainty, both the estimated Swiss toll and the death rate were of a similar magnitude to those in 2003. The comparison is provisional, however: the 2026 figures cover May to August, whereas the historical figures include September.
The Swiss estimates combine daily mean temperatures recorded by MeteoSwiss with preliminary mortality data from the Federal Statistical Office. The model accounts for delayed effects of heat over seven days. September was excluded because its mortality data were too incomplete.
Final figures are due in spring 2027. They will include September, breakdowns by age, sex, region and canton, and a comparison with the Federal Statistical Office’s mortality monitoring. That monitoring identifies periods of excess mortality but does not use temperature data and cannot directly attribute deaths to heatwaves.
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