Mervelier in the canton of Jura recorded a high of 16 degrees, making it the country’s hot spot, according to MeteoNews.
Zurich was not far behind with a top temperature of 15 degrees, ahead of Movelier (Jura), Winterthur (Zurich) and Liestal (Basel Country), where the mercury reached 14 degrees.
Readings averaged up to 12 degrees in the plateau and Lake Geneva basin regions, MeteoNews said, although no records were set.
The mildness even extended into Alpine areas such as Grächen in the canton of Valais, which recorded a high of 11 degrees at an altitude of 1,620 metres.
A current of warm air from the south and southwest originating in North Africa was responsible for the exceptional conditions, weather experts said.
The relatively balmy conditions contrasted with a brutal cold snap in the United States that put half the American population under a wind chill warning.
With temperatures sinking below minus 20 in Chicago and other cities, residents there were warned that if they went outside exposed skin could freeze.
Switzerland’s early spring is expected to continue until at least Thursday when even warmer temperatures could be recorded.
Forecasts call for colder conditions to return on Friday and Saturday.
Meteorologist Ivo Sonderegger told Blick that though it’s been warm this is not unusual for January based on the past few years.
“In the last 10 years we have regularly had relatively high temperatures in Switzerland — practically every second day.”
The readings fall short of records set between 1991 and 1993.
While it reached almost 13 degrees in Basel on Tuesday for example, the high for January in that city is 19 degrees, according to MeteoNews.