Regions with a polar climate are characterized by a lack of warm summers (specifically, no month having an average temperature of 10 °C or higher). Regions with polar climate cover over 20% of the earth. The sun shines 24 hours in the summer, and barely ever shines at all in the winter (see midnight sun and polar night). Polar climate results in treeless tundra, glaciers, or a permanent or semi-permanent layer of ice.
On Earth, the only continent where the extreme (EF -- ice cap) polar climate is predominant is Antarctica. All but a few isolated coastal areas on the island of Greenland also have the extreme EF polar climate. Coastal regions of Greenland that do not have permanent ice sheets have "only" the less extreme tundra (ET) climates. The northernmost part of the Eurasian land mass, from the extreme northeastern coast of Scandinavia and eastwards to the Bering Strait, large areas of northern Siberia and Northern Iceland have tundra climate as well. Large areas in northern Canada and northern Alaska have tundra climate, changing to ice cap climate in the most northern parts of Canada. Southernmost South America (Tierra del Fuego where it abuts the Drake Passage and such subantarctic islands such as the South Shetland Islands and the Falkland Islands have ET, or tundra climates of slight thermal range in which no month is as warm as 10°C. These subantarctic lowlands are to be found more equatorward than the coastal tundras of the Arctic basin.
In other parts of the world, many mountains have a climate where no month having an average temperature of 10 °C or higher, but as this is due to elevation, this climate is referred to as Alpine climate.
Some parts of the Arctic are covered by ice (sea ice, glacial ice, or snow) year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface. Average January temperatures range from about −40 to 0 °C (−40 to +32 °F), and winter temperatures can drop below −50 °C (−58 °F) over large parts of the Arctic. Average July temperatures range from about −10 to +10 °C (14 to 50 °F), with some land areas occasionally exceeding 30 °C (86 °F) in summer.
The Arctic consists of ocean that is nearly surrounded by land. As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). In winter, this relatively warm water, even though covered by the polar ice pack, keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic. In summer, the presence of the near-by water keeps coastal areas from warming as much as they might otherwise, just as it does in temperate regions with maritime climates.
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