What Is The First Day Of Fall. In the northern hemisphere, the september equinox marks the first day of fall. The autumnal equinox, explained this year, the autumnal equinox will begin on sept.
Today is the fall equinox and first day of autumn, when the sun rises directly in. In 2024, the autumnal (fall) equinox arrives on sunday, september 22, marking the official first day of fall.