Tiedote - A record mild December ended an unusually warm year 2006

Photo: Eija Vallinheimo

"In 2006, the mean temperature in the whole of Finland was about one degree higher than the average for the period 1971-2000," says Senior Meteorologist Anneli Nordlund. "The mean temperature ranged from just under 7° C on the southern coast to -0.7° C in Northern Lapland. The year was among the 15 warmest years during a period extending over a century, from the early 1900s to the present," Anneli Nordlund clarifies.

Exceptionally warm from June onwards

"The mild beginning of the year was followed by fiercely cold but sunny weather in all of Finland from the end of January to late March," Anneli Nordlund describes.

"Even in early April, it didn't feel like spring in Southern Finland, because the cloudy weather kept temperatures close to the freezing point. Spring weather didn't arrive in the whole country until late April."

The first hot days were already experienced in early May. The 7th of May, when the temperature reached 25.8° C in Salo, was the warmest day during the whole month Temperatures exceeding 25° C were measured on 59 days during the summer throughout the country, and there were days in June, July and August when temperatures exceeded 31° C. "This is very unusual. 30 degrees is reached in each of the three summer months on average only once in ten years," Anneli Nordlund comments the temperatures.

Summer weather faded slowly during September. However, temperatures approaching 25° C were still measured in Western Finland in late September. The unseasonably warm weather continued in early October. Night frosts arrived in Lapland soon after mid-October.

According to the Finnish Meteorological Institute's measurements, the thermal growing season was slightly longer than usual, but the temperatures were record high. The sums of effective temperature reached new records everywhere. The lengths of the thermal seasons were far from typical (see Table 1): the spring was short and the summer long in Southern Finland.

Thermal winter (daily mean temperature below 0° C) prevailed in almost all of the country for over two weeks at the turn of October-November. "After that, the rest of the year was unusually mild. Thermal winter did not start again on the southern coast until after mid-January 2007."

Records were broken in December: Throughout Finland, the mean temperature for the month was as much as 7-8 degrees higher than the average for the reference period 1971-2000. "According to extreme value calculations, such mean temperatures occur in the current climate a couple of times in a millennium. The temperatures of December 2006 will become quite common by the year 2100 unless climate warming can be halted," Anneli Nordlund stresses.

Exceptionally dry summer, wet autumn

A steady high pressure made the summer of 2006 the driest ever experienced in Southern and Western Finland and on the northern shores of the Gulf of Bothnia. The number of sunny days was one-third higher than the average in many parts of the country. Dryness left its marks on nature, and groundwater levels were low. The longest uninterrupted rainless period, over four and a half weeks, was measured, for instance, in Kauhava in Southern Ostrobothnia.

At the end of September, the sum of precipitation for the thermal growing season ranged from 160 millimetres to over 300 millimetres in easternmost Finland. Thus, in the driest areas, precipitation was only about half of the average value.

Heavy rains in October soaked the soil, and rivers and lakes were filled even in the dry regions. October was the rainiest month of the year. Precipitation in Southern Finland was 2.5 times the average.

The first snow in Lapland fell in late October. It snowed many times around the turn of October-November, and almost the whole country was covered with snow. The snow cover of 20 to 50 centimetres that hand accumulated on both sides of the Salpausselkä ridge in Southern and Central Finland was unusually thick considering the time of the year. However, the very mild weather during the latter half of November melted all of the snow everywhere except in Lapland.

"Even at the end of the year, there was no snow on the ground south of the line extending from Lappeenranta to Kokkola, and the snow cover was almost nonexistent in Eastern Finland as well," Anneli Nordlund explains. "Only in Northern Lapland was the snow cover nearly half a metre thick."

There were only 14 stormy days at sea during 2006, whereas the annual average is 24. There were also few thunderstorms, lightning strokes and whirlwinds during the year.

The strong thunderstorms on 10 July were accompanied by exceptionally large hailstones, up to 6.5 centimetres in diameter. Such large hailstones are seen anywhere in Finland on average once in a decade.

Figures for 2006

Lowest temperature

-43.6° C

20 January, Kittilä Pokka

Highest temperature

32.1° C

8 July, Lammi Evo and Suomusjärvi Taipale

Highest number of hot days

37

The last hot day of the summer season

25.6° C

27 August, Kauhava

The longest thermal summer during the period 1961-2006

160 days

Helsinki-Vantaa

New record for precipitation in October in the whole of Finland

228 millimetres

Vihti Hiiskula

The lowest precipitation in June-August

24 millimetres

Simo Maksniemi and Simo Simoniemi