Winter officially begins on Sunday, Dec. 21, 2025, marking the winter solstice — the shortest day and longest night of the year. That’s the moment when the Northern Hemisphere tilts farthest from the sun, signaling the true start of winter even if the cold has already arrived.

What happens during the winter solstice?

The solstice happens due to Earth’s 23.5-degree axial tilt. At this moment, the sun is directly above the Tropic of Capricorn, its southernmost point. As a result, the Northern Hemisphere experiences its least daylight and the sun appears lower in the sky, offering less warmth.

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