Climate of Finland

The climate of Finland is influenced most by its latitude: Finland is located between 60 and 70 N. Because of Finland's northern location, winter is the longest season. Only on the south coast and in the southwest is summer as long as winter. On average, winter lasts from early January to late February in the outermost islands in the archipelago and the warmest locations along the southwestern coast – notably in Hanko – and from early October to mid May in the most elevated locations, such as northwestern Lapland and the lowest valleys in northeastern Lapland. This means that southern portions of the country are snow-covered about three to four months of the year, and the northern for about seven months. The long winter causes about half of the annual 500 to 600 millimetres (19.7 to 23.6 in) precipitation in the north to fall as snow. Precipitation in the south amounts to about 600 to 700 millimetres (23.6 to 27.6 in) annually. Like that of the north, it occurs all through the year, though not so much of it is snow.^[1]

In Köppen climate classification Finland belongs to the Df group (continental subarctic or boreal climates). The southern coast is Dfb (humid continental mild summer, wet all year), and the rest of the country is Dfc (subarctic with cool summer, wet all year).^[2][3]

The climate of Finland has characteristics of both maritime and continental climate. The Atlantic Ocean to the west and the Eurasian continent to the east interact to modify the climate of the country. The warm waters of the Gulf Stream and the North Atlantic Drift Current, which continuously warm the region, play a big role in the climate of Norway, Sweden and Finland; if it weren't for these currents, the winters in Scandinavia and Fennoscandia would be much colder. Westerly winds bring the warm air currents into the Baltic areas and to the country's shores, moderating winter temperatures, especially in the south and southwest in cities like Helsinki and Turku where winter highs tend to be between 0 and 5 °C (32 and 41 °F) but a cold snap like the one that occurred in mid-January 2016 can cause temperatures to plunge well below −20 °C (−4 °F). These winds, because of clouds associated with weather systems accompanying the westerlies, also decrease the amount of sunshine received during the summer. By contrast, the continental high pressure system situated over the Eurasian continent counteracts the maritime influences, occasionally causing severe winters and high temperatures in the summer.