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March cold snap

Even though, climatologically speaking, winter finishes at the end of February, wintry conditions in the first half of March are very much a feature of the Swiss climate, even in the lowlands on the northern side of the Alps. A cold snap in March is an even more common weather occurrence at higher elevations.

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A regularly occurring weather pattern or singularity is defined as a deviation from the average annual course of meteorological elements that occurs on certain days in the annual calendar with reasonable regularity. The phenomenon of the March cold snap can be identified by the number of days on which snow falls (fresh snowfall events). Fresh snowfall becomes a less frequent occurrence by the end of February at the weather stations in eastern Switzerland (Einsiedeln, Elm, Lucerne, St. Gallen and Zurich). In the first few days of March, however, the number of fresh snowfall events picks up again until 6th March, both in the lowlands and all along the northern slopes of the Alps, up to an elevation of around 1,000 metres above sea level. An extreme cold snap with record-high snow levels was seen in the lowlands on the northern side of the Alps on 4th and 5th March 2006.

Line graph showing the mean number of fresh snowfall events per day between 1st January and 31st March in the period of 1931–2020 in eastern Switzerland. The curve fluctuates between 12 and 31 events from January to February. In the final week of February, the curve falls sharply, then rises to 24 incidences again around 6th March, before falling again.
Number of fresh snowfall events per calendar day in the period of 1930–2020 in eastern Switzerland (mean of Einsiedeln, Elm, Lucerne, St. Gallen and Zurich weather stations). (© MeteoSwiss)

March cold snap more common at higher elevations

The climatological phenomenon of a cold snap in March is even more common at higher elevations. The 100+ year snow measurement series from Arosa (at 1,880 m.a.s.l.) shows fresh snowfall to be a much more common occurrence between 1st and 7th March than in the second half of February or the subsequent weeks in March.

Line graph showing the number of fresh snowfall events per day between 1st January and 31st March in the period of 1890–2020. The curve fluctuates between 38 and 72 events from January to mid-February. Around 10th February, the figure is approximately 60. The number of events then falls to around 45 by the end of February. From 1st to 7th March, the curve fluctuates around 54 to 66 events, before decreasing again.
Number of fresh snowfall events per calendar day in the period of 1890–2020 at the Arosa weather station (1,880 m.a.s.l.). (© MeteoSwiss)

March cold snap signals end of winter in the lowlands

In the lowlands on the northern side of the Alps, the frequency of fresh snowfall decreases rapidly after the March cold snap. In the last third of March, the weather station in Lucerne sees fresh snowfall only about once every 10 to 20 years. However, that does not rule out the possibility of snow falling after this date. The changeable month of April is known for bringing the occasional blanket of snow to the lowlands on the northern side of the Alps. However, the snowfall is usually light, and melts again after a few hours.

Line graph showing the number of fresh snowfall events per day between 1st January and 31st March in Lucerne from 1883 to 2020.
Number of fresh snowfall events per calendar day in the period of 1883–2020 in Lucerne (454 m.a.s.l.). (© MeteoSwiss)