The official start of fall in 2025 is on Monday, September 22. This date corresponds to the autumnal equinox, which is when the Sun crosses the celestial equator and day and night are approximately equal in length. Fall lasts until December 21, which is when winter begins. This applies to the Northern Hemisphere; in the Southern Hemisphere, this date marks the beginning of spring. The specific time of the equinox in 2025 is September 22 at 18:19 UTC. There is also a meteorological definition of fall used by some, which consistently marks the start of fall as September 1 and ends it on November 30. However, the most widely recognized official start is the astronomical one marked by the autumnal equinox on September 22, 2025.
