The mercury hit 20.9°C (69.6°F) in the town of Delémont in canton Jura in northwest Switzerland.
The previous January high north of the Alps had been 19.4°C, recorded on January 12, 1993 in Lucerne. The highest January temperature ever recorded anywhere in Switzerland was 24°C, recorded in Locarno-Monti (2007) and Lugano (1944) in the south of the country.
MeteoSwiss said the record January temperature in Delémont was caused by warm winds from the southwest combined with the Föhn wind – a dry, warm, downslope wind – coming off the Jura mountains.
Other locations saw balmy conditions on Sunday. In Vevey on Lake Geneva, people queued for ice creams, while in Geneva swimmers enjoyed the traditional New Year’s Day dip in the lake with fancy dress and champagne.
In the Rhine Valley of St Gallen and in Liechtenstein, it was also warm on Sunday (18.5°C in Bad Ragaz and 20°C in Vaduz).
A January record high was also set in Altdorf, canton Uri, where the mercury reached 19.2°C on Sunday. The previous cantonal record was 18.5°C.
The mild weather in Western Europe is partly due to warm air from the Atlantic east of the US state of Florida. A similar phenomenon occurred last year, SRF Meteo said.
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