Winter, the cold season of the year. Astronomically, in the Northern Hemisphere winter begins at the winter solstice, about December 22, and ends at the spring equinox, about March 21. Practically, however, the farther north, the longer the winter. In Great Britain, November, December, and January are considered winter months; in the United States, the season includes December, January, and February. In the Southern Hemisphere, winter begins when the northern spring is at an end, and is most severe during June, July, and August.