Fall, or autumn, officially starts in the Northern Hemisphere with the autumnal equinox, which in 2025 falls on Monday, September 22. This is the astronomical definition of fall, where day and night are nearly equal in length. In 2025, fall will end on Sunday, December 21. Alternatively, meteorologists define fall as starting on September 1 and ending on November 30 to align with calendar months. This meteorological fall start is widely used for weather statistics and forecasts. To summarize:
Definition| Fall Start Date (Northern Hemisphere)| Fall End Date
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Astronomical Fall| September 22, 2025| December 21, 2025
Meteorological Fall| September 1| November 30
The astronomical start is based on Earth's position around the Sun (autumnal equinox), while the meteorological start is based on fixed calendar months.
