Lapland's climate is a result of its Nordic location, the Gulf Stream, Arctic Ocean, Bothnian Bay, and tilt of the earth in relation to the sun. This causes the distinct differences between the four seasons of the year. Winter lasts for about 6 months, and the other half of the year is divided between spring, summer, and autumn. By clicking the links to the website of the Finnish Meteorological Institute, you can find municipality-specific weather, snow, and rain reports.

Winter

 As a result of the shortening of days in the autumn, the weather turns colder. The Polar Night starting at the end of November is a period during which the sun will only appear daily for brief moments above the horizon. The closer you go to the North Pole, the less you will see the sun. In Utsjoki, the northernmost municipality of Finland, the sun does not appear at all near the turn of the year. The Winter Solstice occurs between 21 and 22 December and is considered the time when midwinter begins.

Spring

 The Polar Night slowly comes to an end as the North Pole turns towards the sun. In Lapland, this means more daylight starting from the beginning of January, when the days are still freezing cold. The vernal equinox occurs between 19 and 21 March, when the length of night and day is approximately the same across the whole planet. As the days become warmer and longer, the snow starts to melt and the spring is on its way.

Summer

 In June, nature starts to blossom. Midsummer and summer solstice occur between 20 and 22 June. The more north you go, the longer the sun will stay above the horizon. In Utsjoki, the sun will shine continuously for about two months during high summer. Nightless nights are the counterpart of the Polar Night.

Autumn

 In August, the first signs of autumn start to appear. The nights grow darker and the air gets colder as the North Pole turns away from the sun. The autumnal equinox occurs between 22 and 23 September. The phenomenon that occurred at the time of vernal equinox will occur again, i.e. night and day across the entire planet will be of roughly the same length. Lapland glows in various colours during the period of autumn and Finnish people call this foliage colour change 'ruska'.

 Sources:
http://www.ursa.fi/
Palsila, Kari (1995) Lapin opas. WSOY. Porvoo.