Switzerland's summer breaks 2003 heat record, with an estimated 1,257 heat-related deaths

Switzerland recorded its hottest summer ever in 2026, surpassing the previous record set in 2003.

High temperatures were linked to an estimated 1,258 fatalities from May through August. 

Here's what to know

The estimated toll amounts to 14 fatalities for every 100,000 residents, representing 5.5% of deaths in that period, according to Swissinfo.

Tamedia newspapers were the first to report the findings. The Federal Office for the Environment and the Federal Office of Public Health commissioned Swiss TPH to carry out the provisional assessment.

Older residents were hardest hit, with people aged 75 and older accounting for around 85% of heat-related deaths. No other natural hazard causes more deaths in Switzerland than heat, Swissinfo noted.

Despite temperatures surpassing the 2003 record, the estimated heat-related death toll and mortality rate were statistically similar to those recorded that year, according to the Swiss TPH assessment, which covers May through August, with September still to be included.

More background

Roughly seven in 10 heat-related deaths occurred on days classified as hot or very hot, based on daily average temperatures.

Days averaging at least 77 degrees Fahrenheit (25 degrees Celsius) but below 80.6 degrees Fahrenheit (27 degrees Celsius) were associated with 485 deaths, while days averaging 80.6 degrees Fahrenheit (27 degrees Celsius) or higher were associated with 400 deaths.

Those thresholds — about 77 and 81 degrees Fahrenheit — correspond to MétéoSuisse heatwave alert levels 3 and 4. Another 373 deaths were associated with moderate heat below 77 degrees Fahrenheit.

Beyond the public health toll, Switzerland's record heat and drought affected communities, farming, businesses, and nature. As Swissinfo observed, extreme weather reduced rivers to trickles and scorched landscapes.

What's being done?

The assessment compared daily temperature measurements from MétéoSuisse with mortality figures compiled by the Federal Statistical Office.

The Swiss government had also anticipated excess mortality from the heatwave, initially estimating around 570 additional deaths among people aged 65 and older.

A consolidated, detailed assessment is scheduled for publication in spring 2027. It will incorporate updated mortality records, including death reports submitted after the provisional data used in the initial analysis.

Where can I learn more?

Extreme heat has brought deadly summers to Switzerland and other parts of Europe. 

• Western Europe recorded its hottest summer ever, with 13 days of very strong heat stress.

• Fossil-fueled warming drove nearly two-thirds of deaths among Europe's 50,000 summer heat fatalities.

• Western Europe's record heat killed at least 35,000, which WHO called a "dress rehearsal."

• Locals scratched "HELP" into weeds after record heat dried a Swiss-border lake.

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