Fall (autumn) starts at different times depending on the definition used:
- Astronomical fall begins with the autumnal equinox, which in 2025 will occur on Monday, September 22. This marks when day and night are roughly equal in length. Astronomical fall then continues until the winter solstice around December 21.
- Meteorological fall is defined by calendar months for ease of weather and climate tracking. According to this system, fall always starts on September 1 and runs through November 30.
- In popular culture in the US, fall often starts after Labor Day (the first Monday in September), aligning with seasonal weather changes and traditions rather than precise astronomical events.
In summary, fall can start from September 1 (meteorological), around September 22 (astronomical), or early September after Labor Day by cultural convention. The most universally recognized official start date is the autumnal equinox in late September.
