When Is The Fall Equinox 2025. It usually occurs around september 23 and signals autumn’s arrival in the northern hemisphere. This is also the first day of spring (vernal equinox) in the northern hemisphere and the first day of fall (autumnal equinox) in the southern hemisphere.
The first day of autumn is in 2025 on september 22 (according to the astronomical definition). The march equinox occurs at 08:58 utc.