when is first day of fall

The first day of fall in 2025 is on Monday, September 22, 2025, at 2:19 p.m. This moment is marked by the fall equinox, when the Sun crosses the Equator, and day and night are approximately equal in length in the Northern Hemisphere. After this date, days start to become shorter until the winter solstice. This is the astronomical start of fall and applies to the Northern Hemisphere specifically. For the Southern Hemisphere, this date marks the start of spring instead.