Vernal Equinox 2024 Uk Weather. The vernal equinox — is an astronomical phenomenon when the sun, in its visible motion along the ecliptic, crosses the celestial equator. The autumnal equinox occurs in september, and in the northern hemisphere this date marks the end of summer and beginning of autumn.

Astronomically, spring typically starts on the day of the vernal (or spring) equinox which falls around the 20 march in the northern hemisphere. This date marks the spring equinox in the northern hemisphere.