According to Meteo Swiss, spring this year was the coldest in 30 years. The mean May temperature across the country was 2.5 ° C below the 1981-2010 norm.
Over the last 30 years, only 2019 and 2013 came close to having May temperatures as cold as they were in May 2021. When chilly May is added to temperatures over the rest of spring 2021, it is coldest spring in Switzerland for over 30 years.
In addition, almost daily rain made May 2021 the second or third wettest May, depending on the region, since measurements began.
The cold wet weather in May 2021 was caused by a low pressure system from the northwest that brought cold moist air from the Atlantic. Over the first 27 days of May 2021, rain or snow fell almost every day across most of Switzerland. Over this period, only the 3rd, 8th and 9th of May we rain-free across most of Switzerland.
Rainfall across Switzerland was more than 135% of the 1981-2010 norm. In Montana in Valais it was nearly 250% higher.
As a result of the cold, Switzerland’s ubiquitous beech trees turned green 4 days later than normal, which is the latest leaf development in the beech since 1991. In addition, sycamore and linden trees turned green 5 to 7 days later than normal.