How many days until winter?

The shortest day of the year

Astronomical winter starts at the December solstice, the moment the Sun reaches its lowest point in the sky at noon. It is the shortest day and longest night of the year in the Northern Hemisphere, which is why it is also called the darkest day of the year. In the US it falls on December 21 in most years, and occasionally on December 22, depending on the year and your time zone. Dates here use US Eastern Time, based on the US Naval Observatory.

How short the day is depends on how far north you live. On the solstice, the Sun is up for roughly:

• Miami: about 10 hours 30 minutes
• Los Angeles: about 9 hours 50 minutes
• New York and Chicago: about 9 hours 10 minutes
• Seattle: about 8 hours 25 minutes
• Anchorage: about 5 hours 30 minutes
• Utqiagvik, Alaska: no sunrise at all. The Sun stays below the horizon from mid-November to late January.

Earliest sunset, latest sunrise

The shortest day does not have the earliest sunset. Because Earth’s orbit is an ellipse and its axis is tilted, solar noon drifts later through December. In most of the US the earliest sunset comes in early December, about two weeks before the solstice, and the latest sunrise comes in early January, after it. So evenings are already getting lighter by the time winter officially begins, while mornings keep getting darker until the new year.

After the solstice

• Days start getting longer straight away, but slowly: only a few seconds a day at first, and only a few minutes in total by New Year’s Day.
• Meteorological winter runs from December 1 to the end of February. It matches monthly weather records, so forecasters call December 1 the start of winter.
• The coldest weeks usually come in mid-to-late January, a month after the solstice, because land and oceans keep losing heat for weeks after the shortest day.
• In the Southern Hemisphere, the December solstice is the longest day of the year and the start of summer.