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2011 – An exceptionally warm year in Northern Finland
09 January 2012
Finnish Meteorological Institute
The year 2011was unusually warm in Southern and Central Finland and exceptionally warm in Northern Finland. From March until the end of the year, or for ten consecutive months, the mean temperatures in Finland exceeded the long-term averages.
The statistics compiled by the Finnish Meteorological Institute show that the mean temperature for the whole of Finland was 1.9° C above the long-term average. An equally high annual mean temperature was measured last in 1989. A warmer year has been measured only once: in 1938. The annual mean temperature ranged from a little over +6° C on the south and southwest coast to a little less than +1° C in Northern Lapland. The greatest difference from the average temperature was recorded in Lapland, where the annual mean temperature was 2–3° C higher than normally.
In many areas of Finland, annual precipitation exceeded the long-term average. However, in some locations, mostly in North Karelia, the figures were about 10 per cent below the average. The highest precipitation, 963 millimetres, was measured in Puolanka, and the lowest, 464 millimetres, in Nuorgam of Utsjoki.
A mass of snow at the start of the year
The year 2011 began with fairly wintry conditions throughout the country. At one point or another during the winter, the thickness of the snow cover was at least 40 cm in virtually the whole of Finland. Especially the southern and eastern parts of the country had clearly more snow than the long-term average. The thickest snow cover in Southern Finland was 92 centimetres, measured in Utti, Kouvola. The greatest snow depth for the whole of Finland was measured in the Kilpisjärvi village centre, where snow thickness peaked at 116 cm in early March.
As to temperature, January was close to the long-term averages although there were regional variations in temperature differences. By contrast, February was unusually cold in places. The mean temperature for the whole of Finland was nearly 6° C lower than normally. The lowest temperature for the winter and for the whole year, -41.8° C, was measured in Naruska, Salla on 18 February.
Owing to the cold December and February, the mean temperature for the winter 2010–2011 was about 3.4° C lower than normally. Thus, the winter was even slightly colder than the previous winter. Precipitation during the winter months in Southern and Central Finland was generally somewhat greater than usually, but precipitation in Lapland remained under 60 per cent of the average precipitation.
Spring started slowly, but picked up speed quickly
The mean temperature for the spring, or the period from March to May, was higher than usually in the whole of Finland. Owing to the snowy and cold winter, thermal spring did not begin yet in March, but thanks to an unusually warm April, spring progressed rapidly from south to north and began in Northern Lapland nearly a month earlier than normally. In fact, April was even exceptionally warm in some regions in the east and north. The mean temperature for April measured in Sodankylä was the highest in the measurement station’s history. Thermal spring was short because thermal summer already began in early May in Southern Finland; this was a couple of weeks earlier than normally.
An unusually warm summer with many thunderstorms
The summer, or the period from June to August, was unusually warm. The mean temperature for the whole of Finland was 2° C above the average. According to statistics, similar mean temperatures occur on average once in 20–30 years.
June started with an exceptional spell of hot weather. Temperatures exceeding 30° C were measured for about a week – on several days in Lapland as well. This was also the time when the year’s highest temperature, +32.8° C, was measured in Meltosjärvi of Ylitornio.
At some observation stations, the summer was the warmest in their measurement history. This was the case, for example, at Kaisaniemi in 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.
The summer saw more lightning flashes than average. In total, about 180,000 ground flashes were registered for Finland’s land areas. This is roughly 40,000 more than usually. Flashes were the most frequent in Western Finland and in Northern Ostrobothnia. Most thunderstorms occurred in June and July, when over 10,000 ground flashes were registered on seven days. This is rather unusual because typically there are only a couple of days like this during the Finnish summer. The thunderstorms in summer 2011 were characterised by heavy rains. In fact, the heaviest rainfall measured within 24 hours was accompanied by thunder and showers at Aapajärvi of Tornio, where the rainfall on 24 July was 121 mm.
Large hail measuring over 2 centimetres in diameter fell on 17 days. The largest hail detected during the summer was 6 centimetres in diameter, measured near Vaasa on 9 July.
A very warm autumn with little snow
The average temperature for the autumn, or the period from September to November, was exceptionally high in Finland. The difference in temperature for the whole country was 3.5° C. Among individual days, especially the last day of September was exceptionally warm. The highest temperature, 22.3° C, was measured in Porvoo; this is the latest date when the temperature has exceeded 20° C in Finland. Early November was also exceptionally warm for the time of the year, and temperature records for November were broken at several observation stations.
Thermal autumn began in mid-September in Central and Northern Finland; this was clearly later than usually. The difference in Central Finland was a couple of weeks; in Northern Lapland about one month.
Thermal winter also started considerably late in the whole country. It began around 9 November in Central and Northern Lapland, which is about one month later than usually. In general, thermal winter had not yet started in Southern and Central Finland by Christmas; thus, in these regions, thermal winter was at least one to two months late.
There was no snow anywhere in Finland at the start of November, which is rare. Similarly, at the end of November, snow covered an unusually small area for the time of the year.
Mild, rainy and stormy December
The year ended with an unseasonably mild and, especially in the south, an exceptionally rainy December. In large parts of the country, the mean temperature was at least 5° C, and in the north even 9° C, warmer than normally. A new record for precipitation in December was also reached. According to preliminary data, precipitation in Kemiönsaari was 190 millimetres, whereas the typical figure for December in Southwest Finland is about 60 mm.
The last weeks of the year were also quite windy. The number of stormy days in the Finnish sea areas was particularly great in December, when storm winds were measured on 11 days. Typically, there are about three stormy days in December. On 26 December, especially the western part of the country was hit by an unusually violent storm, followed by wind damage on the very next day throughout Finland, with the exception of Lapland.