Temperatures are dropping across the U.S., as the first day of winter, also called the winter solstice, takes place this week across the country and the Northern Hemisphere.
The event begins at 4:48 p.m. ET on Wednesday, Dec. 21, according to the U.S. Naval Observatory.
On the day of a solstice, the Earth is at its maximum tilt, 23.5 degrees, either toward or away from the sun.
A winter solstice happens in the Northern Hemisphere when the hemisphere is tilting away from the sun, making it the day with the least amount of sunlight. The sun is above the Tropic of Capricorn in the Southern Hemisphere and runs through Australia, Chile, southern Brazil and northern South Africa, according to the National Weather Service.
