Fall in America officially begins with the autumnal equinox, which in 2025 falls on Monday, September 22. This marks the moment when day and night are approximately equal in length. The fall season then lasts until the winter solstice, which in 2025 will occur on Sunday, December 21. There are two common ways to define fall:
- Astronomical fall starts at the autumnal equinox (around September 22-23) and ends at the winter solstice (around December 21-22).
- Meteorological fall is defined by calendar months and runs from September 1 to November 30.
While meteorological fall has already started in early September, the official seasonal start accepted by NASA and astronomers is the autumnal equinox, September 22 in 2025, with fall ending at the winter solstice on December 21.
