When Is Autumn 2025 Uk. There are three main different ways of defining autumn:. According to the meteorological season, autumn always starts in the northern hemisphere on september 1 and ends on november 30.

The autumn equinox falls on saturday 23 september this year and marks the day when day and night are roughly equal length. According to the astronomical autumn, the autumn equinox will signal the start of the season and begin on the 22nd of september 2025.