October has seen day after day of temperatures reaching 20 degrees and above. Delémont, in the canton of Jura, enjoyed an unseasonable 25 degrees on Monday.
“That is exceptional for October,” Roland Mühlebach of meteorological service Meteo Schweiz told the Blick newspaper.
Normally the autumn month is known for fog in low-lying areas and sun in the mountains.
“The normal rule of thumb is grey below and blue above,” the meterologist said, attributing the good weather to extremely dry air and the absence of the typical cold bise wind.
October 2017 is on course to become the second warmest ever in Switzerland.
The warmest October on record is 2011 when the average temperature was measured at 13.3 degrees. This year's average so far is 12.4 degrees.
“Because of the cold snap to come we will not match 2011's level this year,” Mühlebach said.
A cold front is set to sweep across the country from the west on Saturday night.
In the space of a few hours, the temperature will drop from 21 to 12 degrees, Meteo Schweiz forecasts.
The cold front will bring rain, and snow will fall at higher levels.
Sunday will be cold, but Monday will see the lowest temperature – 10 degrees – before the thermometer starts to show a return to much warmer weather from Tuesday.
Mühlebach had good news for hikers: “From Wednesday the weather will be ideal for hiking in the mountains, with good visibility,” he told the Blick.