winter

Winter is one of the four temperate seasons, typically characterized by cold weather, shorter days, and the lowest sun angle of the year. In many regions, winter brings snow or frost and influences ecological processes, human activity, and energy use. The transition into winter is defined in two main ways: meteorological, based on monthly temperature patterns, and astronomical, based on the position of the sun relative to the Earth's orbit.

Across the globe, winter occurs at opposite times in the two hemispheres: in the Northern Hemisphere it spans roughly December to February (astronomical winter begins at the winter solstice); in the Southern Hemisphere it spans June to August. In tropical regions, winter is less pronounced and often defined by a dry or cooler season rather than by cold weather.

Weather phenomena vary widely; conditions may include snowfall, ice, freezing fog, frost, and low temperatures. Snow cover can affect albedo and soil temperature; storms and cold snaps can influence transportation, agriculture, and infrastructure.

Ecology and biology respond to winter with dormancy, reduced activity, or migration. Many animals seek shelter or hibernate; some plants shed leaves or enter dormancy. Seasonal changes also affect human systems such as energy demand, heating, clothing choices, and seasonal affective disorders.

Historically and culturally, winter features in festivals and traditions tied to solstices and holidays such as Christmas, Hanukkah, and the New Year. The etymology of the word winter derives from Old English wintr, related to German Winter, from Proto-Germanic *wintruz, linked to the concept of cold seasons.