Winter begins at the winter solstice. In the Northern Hemisphere the winter solstice is usually December 21 or December 22. In the Southern Hemisphere the winter solstice is usually June 21 or June 22.
Some animals hibernate during this season. In temperate climates there are no leaves on deciduous trees. People wear warm clothing and eat food that was grown earlier. Some use sleds or skis. Holidays in winter for many countries include Christmas and New Year's Day.
The name comes from an old Germanic word that means "time of water" and refers to the rain and snow of winter in middle and high latitudes.