US Trends

when is winter

Winter has two common “start dates” depending on which system you use and which half of Earth you’re in.

Northern Hemisphere

  • Meteorological winter (used by weather/climate experts):
    • Starts: December 1
    • Ends: Last day of February (Feb 28 or 29)
    • This lines up with the coldest three months: December, January, February.
  • Astronomical winter (based on Earth’s orbit and the Sun):
    • Starts: On the December solstice (around December 21–22 each year)
    • Ends: On the March equinox (around March 19–21).
* Example: In 2025, one reference city (New York) has astronomical winter starting December 21, 2025 and lasting about 89 days.

So if you’re in places like the US, Canada, Europe, or most of Asia, people might say “winter starts” either on December 1 (meteorological) or around December 21 (astronomical).

Southern Hemisphere

  • Meteorological winter :
    • Starts: June 1
    • Ends: August 31.
  • Astronomical winter :
    • Starts: June solstice (around June 20–21)
    • Ends: September equinox (around September 22–23).

This applies to countries like Australia, New Zealand, and South Africa.

Why there are two answers

  • Meteorological seasons use fixed three‑month blocks to make climate statistics and forecasts easier and to match typical temperature patterns.
  • Astronomical seasons use the exact position of Earth around the Sun (solstices and equinoxes), so the dates can shift by a day or so each year.

In everyday conversation, people mix both systems, but weather services often talk about winter starting on the first of the winter month set (Dec 1 or Jun 1).