Autumn Equinox 2025 Countdown 2025. The autumnal equinox, or the first day of fall in the northern hemisphere takes place every year on september 22nd or september 23rd. It’s one of two days in the year when the sun crosses the celestial equator,.

Autumn equinox 2025 (beginning of astronomical autumn) on the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator,. Fall equinox in the northern.