Summer in Lapland starts about one month later and ends a month earlier than the south coast.
The regions north of the Arctic Circle are characterized by "polar days", when the sun does not set at all.
It thus takes about two months for winter to proceed from Lapland to Åland.
The sea and large lakes slow down the progress of winter.
The northernmost parts of Finland have 73 such days every year.
Even in southern Finland, the longest day (around Midsummer) is nearly 19 hours long.
In summer the mean daily temperature is consistently above 10°C.
Summer usually begins in late May in southern Finland and lasts until mid-September.
The annual changes in temperature are of crucial importance for Finland's climate.
Open areas lose their snow cover within two to three weeks of the beginning of spring, whereas on average the snow in the forest smelts about two weeks later.
The lakes usually become ice-free soon after the growing season begins in April in southwestern Finland, in May in the interior and in June in Lapland.
In the northernmost corner of Finland, the polar night lasts for 51 days.
In southern Finland, the shortest day is about 6 hours long.