Autumn Equinox: When Does UK Autumn Start in 2023?

When does autumn start in the UK?

The first day of autumn all depends on what calendar you follow. According to the meteorological calendar, the first autumn day is Friday 1st September 2023. However, the astronomical calendar is based on the position of the Sun in relation to the Earth and changes each year — known as the autumn equinox. This year, it falls on Saturday 23rd September 2023.

According to the RMG, there is also a third way of defining autumn, known as phenological indicators. This is where events, such as leaves falling off the trees and the migration of birds, indicate that autumn has started. This is greatly influenced by weather and climate, causing autumn to start earlier or later than standard definitions.

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What happens on the autumnal equinox?

The autumn equinox marks the start of autumn as the night becomes longer than the day. According to the Met Office, day and night will be around the same length which is evident in the word's origin derived from the Latin equi (meaning 'equal') and nox (meaning 'night').

"On the autumn equinox, day and night are of roughly equal length and the nights will become increasingly longer than the days," explains the Met Office. "Until the spring equinox, when the pattern is reversed. It also marks the time of year when the northern hemisphere begins to tilt away from the Sun, resulting in less direct sunlight and consequently the cooling temperatures."

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When does autumn end?

The autumn season is defined by three months: September, October and November. According to the meteorological calendar, autumn this year will end on Thursday 30th November 2023. Meanwhile, if you follow the astronomical calendar, autumn will end on Friday 22nd December 2023.

Time to clean off your welly boots and head out on an autumn walk...