September was warmer than usual and extremely rainy in places
According to the FMI statistics, September was warmer than usual throughout the country: the deviation from the climatological normal period 1991–2020 was 1–1.5 degrees Celcius in many places. The average temperature in September varied from approximately 14 degrees on the southern coast to approximately 7 degrees in northern Lapland. The average temperature for the entire country was 10.3 degrees.
The highest temperature in September, 21.8 degrees, was recorded on 2 September at the Tulkkila observation station in Kokemäki. The lowest temperature for the month, –6.4 degrees, was in turn recorded on 7 September at the Oustajärvi observation station in Muonio.
Hot days were no longer observed in September. September heat waves typically occur in Finland approximately every three or four years.
An exceptionally large number of rainy days in places
The amount of precipitation in September was higher than usual in many areas. In particular, the area extending from North Savo and North Karelia to North Ostrobothnia had exceptionally or record-breaking high precipitation levels in some places. A few observation stations measured station-specific records for precipitation in September: the record was exceeded at the observation stations of Ylä-Luosta in Rautavaara (123.7 mm), Mujejärvi in Nurmes (138.9 mm) and Särkijärvi in Utajärvi (142.6 mm).
The amount of rainfall was also reflected in the number of rainy days, which was higher than usual across the country, except for northern Lapland. In September, many places saw precipitation on 20 days. The highest number of rainy days were observed in Koli, Lieksa, where precipitation was received on 27 of the 30 days of the month. This is the highest number of rainy days in September in the 58-year measurement history of the observation station.
According to preliminary data, the highest amount of precipitation in September, 167.9 millimetres, was recorded in Mustavaara, Ristijärvi. The lowest amount of precipitation was received at the Sälgrund observation station in Kaskinen, where the monthly rainfall was 31.0 millimetres. The largest amount of precipitation in a single day, 46.6 millimetres, was recorded at the Rankki observation station in Kotka on 11 September.
Greatest amount of sunshine on the southern and western coast
The number of sunshine hours in September varied between 80 and just under 200 hours, which is usual or slightly less than usual. The largest number of sunshine hours was recorded on the southern and western coast.
Approximately 1,200 cloud-to-ground lightning strikes were observed in September, which is approximately half of the usual number of cloud-to-ground lightning strikes in September.
Further information:
Weather statistics from the Climate Service, tel. +358 600 1 0601 (€ 4.06/min + local network fee)
