This report provides a description of the snow conditions in Sweden during the winters of 1904/05 to 2013/14. In particular, maximum accumulated snow depths, number of days with snow cover and large snow depth increases during one day are studied. Snow depth records for different months and parts of the country have been compiled. Severe snow winters are described and also examples of extreme snowfall and snow depth with return periods of 10 and 50 years are given.
A comparison during the period 1991-2014 to 1961-1990 shows that maximum snow depth decreased in almost the entire country except for northern Norrland. In southern Norrland and northern Svealand, except for the mountains, there has been a statistically significant reduction estimated to 10-20 cm. The number of days with snow cover of at least 1 cm has also decreased in almost the entire country when comparing the two periods. The largest decrease of more than 20 days occurs in parts of southern and central Sweden, a reduction that is statistically significant in these areas.
The maximum official snow depth measured by SMHI is 327 cm on 28 February 1926 in Kopparåsen about 15 km east of Riksgränsen in Lapland. However, there is a suspicion that the snow may have blown in from the nearby mountain. The maximum snow depth in Svealand is 187 cm measured in Ulvsjö in Dalarna on 16 March 1951. The maximum snow depth in Götaland is from Ödskölt in Dalsland on 27 March 1951, when 146 cm was recorded.
Large snow depth increases from one day to the next are often the result of "snow cannons" that can form over the Baltic Sea as a result of winds from the east. This phenomenon is the combination of cold air and the relatively warm sea water that creates heavy snow showers formed in long strips along the wind direction. The air closest to the surface of the water heats up, transferring moisture from the sea into increased humidity that falls as snow when the winds reach land. Especially affected by snow cannons are the Norrland coast from Skellefteå to Gävle, but also the coast of Småland and the large lakes Vänern and Vättern can be affected. For example, snow depth increased 72 cm in Oskarshamn in one day (Jan 1985), 73 cm in Gävle (Dec 1998) and 75 cm in Kilagården (Dec 2012) due to snow cannons. The largest 1-day increase of snow depth that we know of, however, is not due to a snow cannon. In Njunjes in Lapland, snow depth increased 109 cm from 31 October to 1 November in 1921.
The winter with most snow accumulation over Sweden as a whole is 1965/66, in terms of maximum snow depth. This winter's maximum snow depth was measured in Storbron near the border to Norway in Dalarna at 171 cm. In Götaland the snow depth was at most more than one meter at several measuring sites. Åmål in Dalsland with 139 cm had the greatest snow depth for this part of the country. Greater snow depths than in the winter of snow were seen in the Swedish mountains during the winter of 1988/89 and 2009/10 was the snow richest winter in Götaland over the period studied.