Switzerland issues highest heat warning for Basel as country braces for 37°C heatwave

The Federal Office of Meteorology and Climatology (MeteoSwiss) issued the warnings on Wednesday 17 June, covering a period from Thursday noon until Tuesday 20:00. Most of the Swiss Plateau, eastern and central Switzerland, the Grisons, Romandy, large parts of Valais, and Ticino fall under alert level 3 of 4, denoting "significant" risk. The highest level, 4, currently applies to the cantons of Basel-Stadt and Basel-Land, where the danger is deemed "high".

Temperature trajectory

Daytime highs will climb steadily through the weekend. According to MeteoSwiss, temperatures are expected to reach 32–34°C on Friday, 33–36°C on Saturday, and 34–38°C by Monday. The hottest stretch runs from Sunday midday through Tuesday evening. A spell of thunderstorms on Friday may bring temporary relief.

What the warnings mean

Level 4 is declared when the mean daily temperature stays at or above 27°C for at least three consecutive days; level 3 kicks in at 25°C over the same period. The alerts apply to areas below 800 metres above sea level. Authorities stress that heat represents a serious threat to people, animals, the environment and infrastructure, with a high risk of circulatory problems and physical discomfort for vulnerable groups.

Official advice

Residents are urged to drink plenty of fluids (at least 1.5 litres a day of unsweetened, non-alcoholic drinks), seek shade, and avoid strenuous activity during the hottest hours. People and animals must never be left inside a parked car.

Escaping the heat

Those looking to cool down are turning to higher ground and water. Roger Perret, a meteorologist at Meteo News, noted that even at 4000 metres the temperature hovers around zero, while at around 2000 metres it reaches approximately 20°C.

“As far as the eye can see, it’s hot.”

Small lakes have already warmed to about 25°C, while large lakes remain 2–3°C cooler than usual. Mountain lakes in the Upper Engadine offer a brisk 13–14°C. Hiking destinations such as the Rigi (expected to reach a pleasant 20°C at the weekend) and the Chasseral in the Jura (around 25°C) are recommended.