When Is Autumnal Equinox 2025. There are three main different ways of defining. The vernal (spring) equinox in the northern hemisphere is the autumnal (fall) equinox in the southern hemisphere and vice versa.
The vernal (spring) equinox in the northern hemisphere is the autumnal (fall) equinox in the southern hemisphere and vice versa. In 2025 the autumnal equinox will occur on 22 september at 18.20 gmt (19.20 bst).