FM I ’ S M O N TH LY C L I MATE B U L L E TI N – S U MM A RY O F M AY 2020
Cool May ended with floods in Lapland Due to the very cold second third of the month, the mean temperature in May remained below the long-term average almost in the whole of Finland. Warmer weather in late May started spring floods in the rivers of Lapland. According to the statistics from the Finnish Meteorological Institute, the mean temperature in May was 1–2 °C below the long-term average in most of Finland. However, along the coast of Gulf of Finland and in some parts of Lapland, the mean temperature was very close to the average. Precipitation levels were mainly below the average in May. Some parts of central Lapland received clearly less than half of the typical amount of precipitation. The lowest level of precipitation in May, only 8.3 mm, was measured in Pello in western Lapland. The rainiest areas were found in the regions of Southwest Finland, Uusimaa and Savonia, as well as in the very northernmost Lapland. In parts of these areas, precipitation levels exceeded the long-term average. The highest level of precipitation in May, 61.4 mm, was measured at Helsinki Airport in Vantaa. The count of sunshine hours exceeded the long-term average in the entire country. In May Day weather was rather cold, particularly during the night. The coldest temperature of the month, -12.6 °C, was measured in Naruska, Salla, on the night of 1 May. As cold temperature as -7.1 °C was measured even as south as in Pyhtää. Already in the following day, weather turned clearly warmer. In general, the first third of May saw rather variable weather with temperatures mainly close to or slightly below the long-term average. On the warmest
days, highest daytime temperatures exceeded 15 °C in the southern and central parts of Finland. A very cold period for the time of year began after the Mother’s Day on 10 May. Associated with the cold front that passed over Finland from the west to east on 11 May, snow fell even in the south. Many locations received a few Salla, Naruska, 1.5. centimeters of snow. In Joutsjärvi, Sysmä, it fell even 15 cm of snow. Cold weather prevailed until 20 May. The cold period was moreover charac- Porvoo, Harabacka, 26.5. terized by occasional hail showers and severe night frosts. Also, wet snow fell even at the southern coast still as late as in the morning of 15 May. After the 20th, weather turned warmer and on the 23rd temperature climbed above 20 °C first time during the year in Finland. Also, thermal summer began widely by the 23rd. The warmest day in May was in many Highest and lowest temperatures locations the 26th. On that day, also the highest temperature of the month, 24.5 °C, was measured in Harabacka, Porvoo. It was almost equally warm in HIGHLIGHTS: MAY 2020 Torne Valley in the 31st. • Globally, May was 0.63°C warmer than the average May from 1981There was still in mid-May one me2010, the warmest May in this data ter of snow on the ground in parts of record. The last twelve-month Lapland. During the warm days in late period was close to 0.7°C warmer than average, matching the warmest May, snow melted rapidly causing unutwelve-month period. sually fierce spring flooding in Kemijoki • Although May was colder than avand Ounasjoki rivers. The water levels erage for Europe, spring was 0.7°C above average. peaked in the turn of May and June.
-12.6 °C
+24.5 °C
Ilari Lehtonen
Source: Copernicus Climate Bulletin ILMASTOKATSAUS 5/2020 | 21
