Winter Solstice 2025: A guide to the shortest day of the year

The years briefest day and longest night are fast approaching. The winter solstice signals the official start of winter, bringing colder temperatures and the holiday season. The phenomenon is caused not by daylight saving time but by the tilt of the Earth.

While the fall-back adjustment of clocks provides more morning light during winter, it also results in earlier nights. Each day in December sees the sun setting sooner, culminating in the shortest daythe winter solstice.

The National Weather Service notes that this occurs when the sun is positioned directly above the Tropic of Capricorn, at 23.5 degrees south of the equator, spanning countries such as Australia, Chile, southern Brazil, and northern South Africa.

In 2025, the Northern Hemisphere will experience the winter solstice on Sunday, December 21, at 10:03 a.m. EST.

The solstice happens because the Earths axis is tilted approximately 23.5 degrees. This tilt determines the solar declination, which is the latitude where the sun is directly overhead at noon. There are two solstices each year: the winter solstice and the summer solstice.

During the winter solstice, the Northern Hemisphere is angled farthest from the sun, producing longer nights and shorter days. The sun appears lower in the sky, giving off reduced warmth and light. After this point, daylight gradually increases, leading up to the summer solstice, which features the longest day and shortest night of the year.

Author: Gavin Porter