It may seem like winter has already arrived with our recent snow, but on the calendar, winter officially starts with the winter solstice. This year, the solstice is Wednesday, Dec. 21 at 1:48 p.m. PST.
December 21 is also the shortest day of the year. In Seattle, the day will only be eight hours, 25 minutes, and 25 seconds long.
How to offset seasonal lack of vitamin D on winter solstice and beyond
The winter solstice is also the longest night of the year. When the sun is out, the day also marks our longest shadow since the sun’s angle above the horizon is at its lowest point.
What is the winter solstice? It is the astronomical moment when the Sun reaches the Tropic of Capricorn in the Southern Hemisphere at 23.5 degrees south thanks to the tilt of the Earth as it rotates around the sun throughout the year.
In contrast for the Southern Hemisphere, the day is their longest time period of daylight, just like we have during our Summer Solstice in mid-June. Also of interest, those above the Arctic Circle have no daylight at all Dec. 21.
From a weather perspective, the seasons lag the winter and summer solstices since it takes time for the sun to warm the Earth’s surface, ground, and water. So our historically coldest month of the year is January even as our daylight hours start to grow. The same goes for July being our warmest month of the year, even as our hours of daylight begin to shrink.
The winter solstice has quite a history over the centuries. Early humans tracked the days by observing the Sun as it cast shadows at different times of the year. Historians believe Stonehenge in England was built to keep track of the Sun’s annual progress across the sky.
Many countries around the world celebrate the solstice, including Europe, Scandinavia, Eastern Europe, Iran, Japan, and parts of Eastern Asia, while in the Southern Hemisphere, many celebrate their Summer Solstice.
After Dec. 21, our daylight hours will begin to grow longer, at first slowly as a matter of seconds, and then by the spring equinox in March, peaking at around three and half minutes per day. The increase of daylight will then gradually slow, ending on the Summer Solstice in mid-June with just over 16 hours of daylight.
As I often joked just after the winter solstice when working at the National Weather Service, summer is coming!
