Polar regions of Earth

Polar regions receive less intense solar radiation than the other parts of Earth because the Sun's energy arrives at an oblique angle, spreading over a larger area, being less concentrated, and also travels a longer distance through the Earth's atmosphere in which it may be absorbed, scattered or reflected, which is the same thing that causes winters to be colder than the rest of the year except in tropical regions.

However, since the polar regions are the farthest from the equator, they receive the weakest solar radiation and are therefore generally frigid year round due to the earth's axial tilt of 23.5° not being enough to create a high maximum midday declination to sufficiently compensate the Sun's rays for the high latitude even in summer, except for relatively brief periods in peripheral areas near the polar circles.

The large amount of ice and snow also reflects and weakens of what weak sunlight the polar regions receive further, contributing to the cold.

Polar regions are characterized by extremely cold temperatures, heavy glaciation wherever there is sufficient precipitation to form permanent ice, short and still cold summers, and extreme variations in daylight hours, with twenty-four hours of daylight in summer, and complete darkness at mid-winter.

Countries with claims to Arctic regions are: the United States (Alaska), Canada (Yukon, the Northwest Territories and Nunavut), Denmark (Greenland), Norway, Finland, Sweden, Iceland, and Russia.