By Monica Wachman
Updated Mar 24, 2022
Latitude lines—great circles parallel to the equator—measure how far a point on Earth lies from the equator. The farther you travel north or south, the higher the latitude.
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The equator sits at 0° latitude, an imaginary line that circles the planet, equidistant from both the North and South Poles.
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High‑latitude regions of the Northern Hemisphere lie between the Arctic Circle (66°33′48″ N) and the North Pole (90° N). This includes portions of Alaska, Canada, Europe, Russia, and Asia.
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In the South, high latitude stretches from the Antarctic Circle (66°33′48″ S) to the South Pole (90° S), encompassing Antarctica.
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In both hemispheres, polar regions experience extended periods of darkness during winter and continuous daylight in summer—a phenomenon known as the midnight sun. The duration of these extremes grows longer the closer one gets to a pole.
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Large body size is common among high‑latitude fauna. A 2010 study in The American Naturalist (Ho, Pennings & Carefoot) found that richer nutrition and reduced heat loss may explain this trend, giving polar animals an evolutionary advantage in cold climates.
