Press release 9.9.2021

Rainy August ends exceptionally warm summer

Even though average temperatures in August were normal, record-high temperatures were recorded in southern and central parts of Finland for the whole summer. For example, in Kaisaniemi in Helsinki the average temperature for the summer was the highest in the weather station's long history. In Anjala in Kouvola there was a record-breaking streak of 31 days in which the temperature exceeded 25 degrees.
Photo: Eija Vallinheimo

According to Finnish Meteorological Institute statistics, the average summer temperature from June through August varied between just over + 18 degrees in the south to + 13 degrees in Northern Lapland. In southern and central parts of Finland new summer heat records were set at many observation stations. For example, in Kaisaniemi in Helsinki the average summer temperature, 18.9 degrees, was the highest since 1844, when keeping records began. In northern parts of the country the summer was mostly unusually warm, which means that such high readings occur less than once every ten years on average.

Measured against the average temperature of the whole country, the past summer was the second warmest in the statistics that have been kept since the early 20th century. The summer was warmer than this year in 1937.

The highest temperature of the summer, 34.0 degrees, was measured on 15 July at the Asemantaus observation station in Heinola. The lowest temperature, -3.6, was measured on 27 August at the Naruska observation station in Salla.

The June-August period had a total of 50 hot days, when the temperature exceeded 25 degrees; the long term average is 33 hot days in a summer. Of the individual observation stations, the greatest number of hot days in June-August was 42, in Anjala in Kouvola. If the hot days in May are included, the total was 43. At the Anjala observation station, hot temperatures were recorded on 31 consecutive days, from 18 June to 18 July, which is the longest unbroken period of temperatures exceeding 25 degrees since 1961.

Summer precipitation was near the average

The amount of precipitation in the summer was largely normal or slightly higher. Lower-than-average levels of precipitation occurred mainly in the southeast of the country and in the northwest of Finnish Lapland. According to preliminary data, the precipitation was highest in the village of Taivalkoski, where it rained 315.6 millimetres in June-August. Precipitation was lowest in the village centre of Kilpisjärvi in Enontekiö, where it rained just 85.4 millimetres.

In lightning, the number of ground discharges in June-August was slightly below 130,000, which is about 7,000 above the average. The Aatu and Paula storms in June helped push the number of ground discharges to above the average level, even though late summer lightning activity was fairly low.

The number of hours of sunshine measured at the observation stations in the summer months was higher than usual.

Only one hot day in August

According to Finnish Meteorological Institute statistics, the average temperature for August varied between about +16 degrees on the south coast and just over +10 degrees in Central and Northern Lapland. In a large part of the country the average temperature was close to the long-term average, or slightly below. The greatest deviations were in the south of the country where the average temperature was about half a degree below average in parts.

The highest temperature in August, 25.7 degrees, was measured on the 13th of the month both at the Anjala measuring station in Kouvola and the Koivuniemi observation station in Virolahti. This was also the only hot day in the month. August typically has nine hot days. The highest temperature of August this year was unusually low. The most recent time that the highest temperature of the month was lower than the highest temperature of August this year was August 2000.

The lowest temperature of the month, -3,6 degrees, was measured on 27 August at the Naruska observation station in Salla.

August was exceptionally rainy in places

August was clearly more rainy than usual in many areas. Especially in an area extending from North Ostrobothnia to Central Finland and North Savo, the amount of precipitation was exceptionally high. It was generally unusually rainy in southern and central areas. The amount of rain was below long-term averages only in the western and northern parts of Finnish Lapland.

The greatest amount of precipitation in the month, 189.8 millimetres, was measured at the Röykkä observation station in Nurmijärvi. The lowest amount of precipitation was at the Kilpisjärvi village centre in Enontekiö - 38.3 millimetres. The greatest amount of precipitation in a single day, 71.4 millimetres, was measured in Kuhmo, at the Kalliojoki observation station on 3 August.

About 13.700 ground discharges were observed in August, which is slightly below half of the average number of lightning strikes.

There were fewer hours of sunlight than usual at weather observation stations.

Further information:

Meteorologists use the word exceptional when the statistical likelihood of a weather phenomenon occurs on average three times or less in 100 years. A phenomenon is called rare if the average occurrence is less than once in ten years.

Climate statistics

Peak hot temperatures in the summer of 2021 (in Finnish)

Weather statistics from the Climate Service, tel. + 358 600 1 0601 (€ 4,01/min + local network fee)