While many people relate the winter solstice as being the shortest day and longest night of the year (which is true), the winter solstice is a moment in time defined by when the northern axis of the Earth is located farthest from the sun.

What the winter solstice really means

The Earth’s poles do not sit directly north and south. Instead, the Earth sits at a constant tilt of about 23.5° off a vertical axis.

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As the Earth rotates, because of this tilt, there are points during our annual orbit around the sun where the Earth’s tilt causes the Northern Hemisphere to be farther away from the sun and points where the Northern Hemisphere is closer to the sun.

As a result, the most direct sunlight shifts between a band of latitudes, specifically between the Tropic of Cancer and Tropic of Capricorn, throughout the year, leading to the change of seasons seen in the middle and higher latitudes.

Since the winter solstice is when the northern axis is farthest from the sun, this also means:

• The sun’s angle is at its lowest point in the sky.
• Days will slowly begin getting longer after the winter solstice
• This marks the beginning of the winter season. (However, if you ask a meteorologist, winter actually started three weeks prior).

The opposite is true in the Southern Hemisphere. Dec. 21 will mark their summer solstice, or longest day of the year. That’s because the southern axis of the Earth will be closest to the sun and their official start to summer.

The winter solstice occurs on either Dec. 21 or 22 nearly every year, though on rare occasions, it can be as early as Dec. 20 or as late as Dec.. 23. The 2025 winter solstice occurs at 10:03 a.m. EST on Dec. 21.