The phrase polar night is often used to mean the middle of winter, including in the south of Finland. However, in reality the polar night refers to the time when the sun does not rise above the horizon at all. Thus, the true polar night can only be experienced north of the Arctic Circle.
The polar night begins in the northernmost parts of Finland and gradually moves south. In Utsjoki the polar night begins at the end of January and lasts 52 days. Further south in Lapland the polar night is shorter. In Sodankylä the polar night begins on 20 December and lasts four days.
Contrary to popular belief, it is not pitch black during the polar night. In the middle of the day there are a few hours of dim light, which, especially on clear days, is a glorious blue. The snow on the ground makes things lighter, and it is helped by the moon, the stars and, sometimes, the Northern Lights. In the light-pollution-free polar night of Lapland the moon is often so bright that you cast a sharp shadow as you walk in the moonlight.
The darkest and shortest day of the winter is the winter solstice, which occurs around 20 December. After this the days begin to lengthen again, and on Christmas Eve the polar night in Sodankylä ends. This does not mean that the sun begins to shine in earnest: it merely peeps over the horizon, generally remaining behind the woods and hills. Only when some time has passed after the end of the polar night can the bright sunlight reach the inhabitants of Sodankylä again.
Tip! If you want to see the sun as early as possible after the polar night, climb to the top of Luosto in the middle of the day to see it.