The Finnish Meteorological Institute to adopt a new normal period for climate statistics
The recent statistics describe the prevailing climatic conditions and form an important base for interpreting the current weather conditions and for monitoring the weather. Climate statistics are also used in research and decision-making, especially in sectors dependent on the weather and the climate.
Climate statistics are calculated globally using weather observations ranging over a 30-year period. The official normal period set by the World Meteorological Organization (WMO) is 1961–1990. However, it is recommended that the statistics be updated, whenever possible, once every ten years. In Finland, the previous update took place ten years ago.
Statistics on various weather factors for individual observation stations
Monthly means and ranges of various weather factors, such as temperature and precipitation, during the new normal period 1981–2010 were calculated for dozens of weather observation stations. Also other data, such as the times when one thermal season changes over to the next and the duration of snow cover, were determined for the new normal period.
The statistical values for temperature at individual observation stations during the new normal period 1981–2010 are typically slightly higher than those during the previous normal period 1971–2000. In the new normal period, the annual mean temperature for the whole of Finland is almost 0.4° C higher than in the previous normal period. The observed rise in temperature is fairly consistent with estimates based on models describing the impact of climate change in Finland.
For precipitation, variation from year to year is greater than for temperature; thus, the differences between the normal periods are not as clear, either. However, the average annual precipitation is slightly higher in the new normal period than in the previous normal period.
Adoption of the new normal period
The new normal period has been adopted in Climate Services, but in practice the maps, tables and other data on our website are being updated gradually throughout the year whenever the information is relevant.
There is one major exception to the adoption of the new normal period. So far, the normal period for calculating the heating degree day is still 1971–2000, because that is the period specified, for example, in the legislation concerning energy certificates of buildings.