The arctic tundra, in the far northern reaches of the Earth, around the North Pole, is characterized by low temperatures and short growing seasons.
The angle of the sun's rays is always low in the tundra. Therefore, it never receives much energy from the sun at any time.
 Summer
In the tundra, summer lasts six to eight weeks.
Summer days are very long. The long days allows enough heat from the sun to build up so that the upper layer of soil can thaw.
The lower layer of soil, known as the permafrost, is always frozen.
Because melting snow cannot drain into the permafrost, water collects on the surface.
Thus, in the summer, the tundra becomes covered in marshes and ponds.
During this short growing season, grasses and sedges become abundant. Low mats of lichens and mosses cover large areas.
Some trees, such as birches and willows grow close to the ground. They rarely grow more than a few centimeters tall.
The leaves of most plants are small. Flowers bloom and quickly develop seeds.
Arctic hares and arctic foxes can be seen in brown coats. (Their coats turn white in winter.)
 Reindeer, also known as caribou, are plentiful.
 Lemmings are also active.
Snowy owls and weasels, which prey on lemmings, can be seen when the lemming population is high.
Winter
When winter arrives, ponds and lakes freeze.
With short days and low temperatures, there is little energy available.
Food is scarce.
Living things become dependent on stored energy for survival.
Almost all tundra plants are dormant in winter.
Many insects remain in the egg or larval stage.
Reindeer migrate southward.
Many birds also travel south.
Lemmings and other small animals burrow under sheltered spots in the snow, where they consume seeds and parts of plants that they stored during the summer.
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Climate