The tundra is the coldest of the biomes. It also receives low amounts of precipitation, making the tundra similar to a desert. Temperatures are frequently extremely cold, but can get warm in the summers.
The winter temperatures are so cold that there is a layer of permanently frozen ground below the surface, called permafrost. This permafrost is a defining characteristic of the tundra biome.
In the tundra summers, the top layer of soil thaws only a few inches down, providing a growing surface for the roots of vegetation.
The tundra is usually a wet place because the low temperatures cause evaporation of water to be slow. Much of the arctic has rain and fog in the summers, and water gathers in bogs and ponds.