410 heat deaths in summer 2025: older people most affected
The federal government estimates the heat's toll from temperature and mortality data. More than half of the attributed deaths fell on days with a daily mean below 25 degrees.
According to the federal government's estimate, the heat caused 410 deaths in Switzerland in summer 2025. It hit the oldest age group especially hard: 84 percent of the attributed deaths were among people aged 75 and over. They make up roughly one tenth of the population. The balance sheet, published on the website of the Federal Office of Public Health, covers the months of May to September 2025, not the summer of 2026.
Nationwide there were 4.5 heat-related deaths per 100,000 inhabitants. Ticino recorded the highest rate at twelve, eastern Switzerland the lowest at two. The differences show how unevenly the burden falls within the country. For a comparison, such population shares are more informative than the mere number of deaths in regions of differing size.
Heat is rarely written on the death certificate
The figure of 410 is a statistical estimate, not a list of individually medically confirmed heat deaths. The report published in July 2026 by the Swiss Tropical and Public Health Institute links measured temperatures with mortality data. For the estimate it gives a 95 percent confidence interval of 284 to 537 deaths.
The model determines how mortality is related to rising temperatures. In doing so it also takes delayed effects of up to seven days into account. The mortality data used are still provisional; later reports may change the results.
That also explains an apparent contradiction: in the weekly mortality monitoring of the Federal Statistical Office, there was no statistically significant excess mortality among people aged 65 and over in summer 2025. That monitoring compares weekly deaths with an expected range. The heat indicator, by contrast, includes daily temperature data and can also capture less pronounced burdens. The two analyses answer different questions.
Moderately hot days count too
According to the FOPH, more than half of the heat-related deaths fell on days with an average temperature below 25 degrees. This refers to the mean of the whole day, not the peak temperature measured in the afternoon. The burden is therefore not limited to individual days with exceptionally high peaks.
The World Health Organization WHO describes how heat stresses the body: when it has to cool itself more strongly, the heart and kidneys, among other organs, are strained. Existing cardiovascular or respiratory diseases and diabetes can worsen. Consecutive hot days and nights increase the cumulative burden. A cool night is therefore more than a question of sleeping comfort: it interrupts the sustained exposure to heat.
Not everyone can protect themselves equally well. Besides age and state of health, according to the WHO, living conditions and access to cool rooms play a role. Physical work outdoors also increases exposure. The number of heat deaths thus describes a health burden that is rooted in very different living and working conditions.
The WHO recommends seeking shade or cool rooms on hot days and regularly contacting particularly vulnerable people nearby. When airing rooms, the temperature difference matters: at night cooler outside air can help, while during the day windows and shading should keep the heat outside as far as possible.
Care settings lack protected spaces
The FOPH commissioned a separate study of what protection looks like in everyday work. In autumn 2025, 900 employees from long-term care, outpatient care and hospitals and clinics took part in a survey. Nine out of ten reported burdensome symptoms at work. Drinking water was usually available; however, according to their responses, cool break rooms, additional breaks or adapted work clothing were often missing.
The responses reflect the experiences of the participants. They are not a full survey of all Swiss care institutions. Nevertheless, they name concrete problems that a general behavioural recommendation to older people does not solve: people who receive care often depend on others for room temperature, daily routine and support.
Among the cantonal authorities, heat protection was also at differing stages of development in 2024. According to the FOPH survey at the time, 18 of 26 health authorities had implemented measures; eight cantons had heat action plans. The ongoing project for implementation in the health sector runs until 2027. It is intended to identify gaps and develop recommendations for those responsible.
Sources
- FOPH: Heat-related mortality, time series to 2025
- Swiss TPH on behalf of FOEN and FOPH: Monitoring summer 2025, July 2026
- FOPH: Heat protection measures and surveys in the health sector
- WHO: Heat and health, 31 July 2026
- Header image: Francesco Piraneo G., Parco Ciani, Wikimedia Commons
- Header image licence: CC BY 3.0
- Article image: Juhanson, Fresh water fountain, Wikimedia Commons
- Article image licence: CC BY-SA 3.0
