In the winter it is so cold that the little snow that does fall doesn't melt - so deep snow covers the land and the ice. Here's a map that shows you how little it gets. This is the Arctic. The Northern summer is short and intense. Plants must complete their flowering cycle in little more than two months.
All plants bloom together, which turns summer into a wonderland of colour.
During the brief summers, the top section of the soil may thaw just long enough to allow plants and microorganisms to grow and reproduce.