From Glossary of Meteorology


  1. Astronomically, between the winter solstice and vernal equinox in the Northern Hemisphere, and the summer solstice and autumnal equinox in the Southern Hemisphere; the coldest season of the year; the "low sun" season during which the sun is over the opposite hemisphere; the "hibernal" season.

    Popularly and for most meteorological purposes, winter is taken to include December, January, and February in the Northern Hemisphere, and in the Southern Hemisphere, June, July, and August; the opposite of summer.