Fall (autumn) begins at different times depending on whether you use the meteorological or astronomical definition.
- According to the astronomical definition, fall in the Northern Hemisphere begins with the autumnal equinox, which in 2025 occurs on Monday, September 22 at 18:19 UTC. This is when day and night are approximately equal in length, and marks the start of the season until around December 21 or 22, the winter solstice.
- According to the meteorological definition, fall starts on September 1 and lasts until November 30. This method divides the year into four fixed seasons based on calendar months for easier climate comparison.
Therefore, fall in 2025 starts either on September 1 (meteorological fall) or September 22 (astronomical fall) in the Northern Hemisphere.
