Geneva recorded an average temperature of six degrees, the warmest since records began, said MeteoSuisse.
The weather station at Sion in the Valais expects an average of four degrees for January, around one degree higher than ever before.
And in many parts both to the north and south of the Alps it's likely to be the second warmest since records began in 1864, added MeteoSuisse.
The higher temperatures are a consequence of frequent storms coming from the west and south-west, said meteorologists. Almost continuous warm air from the Atlantic has raised temperatures and prevented cold air from stagnating on the Swiss plains, which is what normally happens in winter.
However it's a different story at altitude, where temperatures have been about normal for the month.
For some parts of the Swiss Alps, January has been characterized by huge amounts of snow that cut off some ski villages on two separate occasions.
Speaking to the Tribune de Genève, meteorologist Didier Ulrich said it's not unusual that an overall warm month should nevertheless bring lots of snow.
“The coldest winters are not those when it snows the most,” he said. “In fact, it all depends on the direction of the winds.”
While normally Switzerland experiences a north-easterly bise in January, bringing cold, clear nights, this month westerly winds from the Atlantic have dominated, “bringing at the same time warmth, clouds and heavy precipitation”, he explained.
Geneva, while warm, had the fifth wettest January since 1864, with twice as much rain as normal, said the paper.
Sion in the Valais, near some the ski resorts rendered inaccessible by snow, saw 200mm of precipitation, four times the norm.
The Grand St Bernard pass at 2,500m altitude saw a whopping 850mm of precipitation in January, where normally it only gets 230mm.
The warm weather is a contrast to January 2017, which was the coldest for 30 years but didn't experience a great deal of snow.