The Finnish Meteorological Institute’s measurements show that the past summer was the fourth warmest since the beginning of the 1900s. The warmest summer was recorded in 1937, when the mean temperature for the whole of Finland was 16.2° C. In 1972, the mean temperature for the summer months was 16.0° C and in 2002 it was 15.8° C. In the summer of 2010, June and late August fairly cool, which lowered the mean temperature to 14.9° C for the whole country. In 2011, all three summer months were unusually warm.
At some observation stations, the past summer was the warmest ever measured. This was the case, for instance, in Kaisaniemi, Helsinki, where observations have been made since the early 19th century. However, owing to urbanisation, the observations made in Helsinki in the 19th century are not fully comparable with the present day. This summer, the number of hot days (temperature over 25° C) was higher than average, but clearly less than in 2010. This year the number of hot days in the whole country was 46, while the typical number is 38. Among observation stations, the highest number of hot days, 36, was measured in Lahti.
The most notable feature of the past summer’s temperatures was the heat wave measured in early June. It was particularly exceptional in Lapland, where such temperatures occur on average only two or three times a century. Temperature records for June were broken in many localities. The highest temperature for the whole summer, 32.8° C, was measured in Meltosjärvi, Ylitornio on 10 June.
In general, the past summer was slightly rainier than average, although there were wide local variations in precipitation. Total rainfall for the summer ranged from 371 millimetres, measured in Paljakka, Puolanka, to 114 millimetres, measured in Isokari, Kustavi. The greatest rainfall within 24 hours was 121 millimetres, measured in Tornio on 24 July.
The number of ground flashes registered in June–August was about 177,000, which is roughly 30,000 more than generally. Unusually many lightning flashes were recorded in June and especially in July, whereas the number of flashes in August fell below the long-term average.
Climate in Finland: