Switzerland has experienced its third-warmest June since records began
Keystone-SDA
Switzerland has experienced its third-warmest June since records began in 1864. The national average temperature was 3.5 degrees Celsius above the 1991–2020 average.
The warmest June on record was in 2003, whilst the second-warmest, according to a report published by the Federal Office of Meteorology and Climatology (MeteoSwiss), was in 2025.
According to meteorologists, the heatwave at the end of the month was, given its combination of duration and intensity, “of historic proportions”. Several weather stations, including those in Basel, Neuchâtel and Zurich, recorded their hottest 10-day period since records began.
The heatwave led to numerous new records. In Basel-Binningen, a new all-time record for German-speaking Switzerland was even recorded at 39 degrees. New station records for the daily maximum temperature were also set in Neuchâtel (38.1 degrees) and Zurich-Fluntern (37.1 degrees), amongst others.
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At the Bern-Zollikofen station, a new record was also set with 13 consecutive days of high temperatures.
The heat also accelerated the growth of vegetation: for example, lime trees in the lowlands flowered on average ten days earlier than the long-term average.
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Highest drought warning
The month was also generally drier and sunnier than the long-term average. In some regions, less than 40% of the usual rainfall was recorded. The rainfall deficit at national level between April 1 and June 28 was more than 170 millimetres.
Due to the persistent drought, the government raised the drought warning level to the highest level for a large part of the country. At four monitoring stations, including Altdorf and Engelberg, it was the driest June on record since measurements began.
Despite the general dry spell, there were severe thunderstorms in some regions. On June 9, a supercell thunderstorm swept across the Mendrisiotto region of Ticino, bringing hailstones with a diameter of four to five centimetres.
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Several Swiss records broken for heatwave duration
At the Coldrerio weather station, 40.9 millimetres of rainfall were recorded within ten minutes – a new record for the southern side of the Alps.
On June 19, a cluster of thunderstorms also brought extreme rainfall to the greater Zurich area. In Zurich-Affoltern, 44.1 millimetres of rain fell within an hour. One person lost their life.
Statistically, such an event occurs in the Zurich region only once every 30 to 50 years, or even less frequently.
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Rare combination of weather events caused Swiss heatwave
Translated from German, sub-edited by mga
