when the first day of fall

The first day of fall in 2025 is on Monday, September 22. This corresponds to the autumnal equinox, which occurs at 2:19 p.m. EDT (18:19 UTC) that day. The equinox marks the moment when the sun crosses the celestial equator heading southward, resulting in nearly equal day and night lengths in the Northern Hemisphere, where fall begins astronomically at this point.