Lugano counts 43 tropical nights this year, with more than 50 expected

In Lugano, the night air hardly cools down any more. Since the start of 2026 the city has recorded 43 tropical nights, meaning nights when the temperature never drops below 20 degrees. Nearby, the Locarno Monti weather station has counted 42.

According to Vincent Devantay, a meteorologist at Meteo News, the tally is set to rise further in the coming weeks: the barrier of 50 tropical nights will be passed before the end of summer.

The phenomenon is not limited to Italian-speaking Switzerland. Vevey, the third-warmest place in the country after nightfall, has reached 35 tropical nights and is approaching the 40 mark. Pully, also in the canton of Vaud, has counted 31, while Neuchâtel stands at 25.

All these towns share one feature: they sit on the shore of a lake. This year the water in Switzerland's lakes has reached unusually high temperatures. It varies little between day and night, preventing the air from cooling below 20 degrees.

Devantay stresses how quickly the situation has changed. «Una ventina di anni or sono, quando ho iniziato a occuparmi di meteorologia, ogni notte tropicale era ancora un evento» (some twenty years ago, when he started working in meteorology, every tropical night was still an event), he recalls. At the time, a single tropical night made the news and special bulletins were prepared for it. In recent years, however, such episodes have multiplied. «Spesso non ci rendiamo conto di quanto sia stato veloce il cambiamento» (we often do not realise how fast the change has been), the meteorologist observes.

Lows approaching 25 degrees

The novelty of this summer is a further step up. In some areas the overnight minimum temperature has come close to 25 degrees. In Vevey, the warmest night was the one between 25 and 26 June, when the thermometer did not fall below 24.8 degrees.

For nights this warm, the language of meteorology has no official definition yet. Devantay suggests some possible terms: "supertropical", "hypertropical" or "extratropical" nights.