The first day of fall in 2025 is on Monday, September 22. Specifically, the autumnal equinox, which marks the official start of fall in the Northern Hemisphere, occurs at 2:19 p.m. EDT (18:19 UTC) on that day. This equinox is the moment when the Sun's center crosses the Earth's equator, leading to nearly equal lengths of day and night.

Additional Details

• The equinox is also known as the autumnal equinox or September equinox.
• Although called "equal night," day is typically a bit longer than night due to atmospheric effects and terrain.
• Meteorologists may define seasons differently based on temperature averages, but astronomically, fall begins at this equinox.
• The autumnal equinox signals shortening days and the transition to cooler weather and changing foliage in many regions.

Thus, for 2025, the official first day of fall is September 22.