Winter 2020 in United States

Winter Starts: Monday, Dec 21 2:02 am PST

Winter Ends: Saturday, Mar 20 2:37 am PDT

Region: Washington/United States

The first day of winter (Winter solstice or December solstice) is when the sun is in its most southern position directly over the Tropic of Capricorn. This is referred to as astronomical winter or the winter solstice.

Astronomical winter starts at different times around the planet because of the different time zones as related to Coordinated Universal Time (UTC, same as Greenwich Mean Time based on the Royal Observatory in Greenwich, London [1]). For countries located west of UTC your winter will start earlier than countries located east of UTC.

Astronomical and Meteorological Winter

Astronomical Winter is determined by the changing positions of the earth relative to the sun giving us the solstices and equinoxes. Seasons are caused by the tilt of the earth on its axis by 23.5 degrees. The tilt of the earth does not change as it goes around the sun so in the Northern Hemisphere the earth is tilted toward the sun in June and away from the sun in December[2]. When the sun is over the equator you have the equinoxes and when the sun is over the Tropic of Cancer in the most northern position you have the summer solstice and conversely when the sun is over the most southern position over the Tropic of Capricorn you have the winter solstice. The winter solstice occurs in the Northern Hemisphere between the dates of December 20 to 23 followed by the March equinox - March 19 to 21 and then the Summer solstice - June 20 to 22 and finally the Autumn equinox - September 21 to 23. The United States, most of North America, Europe and many countries in the Northern Hemisphere use astronomical winter to determine when winter season officially starts and ends.

Meteorological Winter is determined by the annual temperature cycles and the Gregorian calendar. Meteorological winter starts December 1st in the Northern Hemisphere and lasts 3 months (December, January, and February) with Spring Season (March, April, and May) and Summer Season (June, July, and August) and finally Autumn Season (September, October, and November). Australia and New Zealand in the Southern Hemisphere use meteorological winter thus the months of June, July, and August to determine their winter season.

Many countries around the world depending on their latitude will use different methods to determine the start of winter. Some of these methods are dependent on ecological reckoning or what ecologists call the start of the hibernal season, which is related to biological dormancy. More on ecological reckoning to determine winter can be found on Wikipedia.org.

References:
1.”Greenwich Mean Time” - Wikipedia, wikipedia.org.
2.”Earths tilt and the Winter solstice” - National Weather Service, weather.gov.

Dates for Winter

Year	Winter Starts	Winter Ends
Winter 2023	Thursday, December 21, 2023	Monday, March 20, 2023
Winter 2024	Saturday, December 21, 2024	Tuesday, March 19, 2024
Winter 2025	Sunday, December 21, 2025	Thursday, March 20, 2025
Winter 2026	Monday, December 21, 2026	Friday, March 20, 2026
Winter 2027	Tuesday, December 21, 2027	Saturday, March 20, 2027
Winter 2028	Thursday, December 21, 2028	Sunday, March 19, 2028