Fall starts in two ways depending on the definition used:

• Meteorological fall begins on September 1, 2025.
• Astronomical fall starts with the autumnal equinox, which in 2025 will occur on Monday, September 22 at 2:19 PM Eastern Time.

Meteorological fall is based on the calendar months (September, October, November), while astronomical fall is determined by Earth's position relative to the sun at the equinox, marking nearly equal day and night lengths. The autumnal equinox is considered the official start of fall in many traditions and marks the transition to shorter days and cooler temperatures.