When Is Autumnal Equinox 2024. Here is what you need to know: A carefully worded answer is that on.

While meteorologists like to call fall at the beginning of september, astronomical autumn starts later, on the autumnal equinox. Autumn equinox 2024 (beginning of astronomical autumn) on the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator, moving from the northern hemisphere to the southern.