Winter is the coldest season of the year. In the Northern Hemisphere, winter weather lasts from December through February. The Southern Hemisphere has winter weather from late June through August. People living in the tropics rarely consider winter a distinct season because the temperatures there change little from month to month. The lowest winter temperatures usually occur in the middle of each continent.
In winter, polar regions become especially cold because the sun does not rise there for weeks at a time. Cold air from these regions moves toward the equator, creating strong cold fronts, the leading edges of cold air masses. Storms that move from west to east develop along cold fronts. In the middle latitudes, winter storms can produce large snowfalls, particularly where the air moves up mountains or crosses an unfrozen lake, dumping lake-effect snow on the shore. In warmer parts of middle latitudes, winter rain often starts as snow that melts on its way to the ground.
See also Blizzard; Season; Sleet; Snow; Wind chill.
