Monday heralds the arrival of the autumn equinox, marking the official end of summer and the beginning of a period where nights will progressively outlast days.
This astronomical phenomenon occurs as the northern hemisphere commences its tilt away from the Sun, a shift that brings about shorter daylight hours and cooler temperatures, according to the Met Office.
During the equinox, the Sun’s rays shine directly onto the equator, resulting in an almost equal duration of day and night across the globe.
While meteorological autumn began on 1 September and concludes on 30 November, the exact date for astronomical autumn can vary each year, typically falling on 22 or 23 September.
The Met Office anticipates more unsettled weather conditions as the season advances.
“Autumn is what we call a transition season between summer and winter, moving towards typically more unsettled weather, but it doesn’t mean we won’t have spells of what people consider warmer weather,” Met Office meteorologist Oli Claydon said.
Equinox today - ‘equal night’ and day. This photo, just taken, clearly shows the Sun’s shadow perpendicular to the equator. Start of Fall in the north, start of Spring in the south.
— Chris Hadfield (@Cmdr_Hadfield) September 22, 2025
(Image GOES-19 satellite @NOAA)https://t.co/4S8rjqZPqM pic.twitter.com/ZANaxxdQei
This week, the weather is expected to be dry and bright for most of the UK, until the weekend when wind and rain are expected to move in, Mr Claydon said.
There have been below average temperatures over recent days, with low temperatures of minus 2.1C on Sunday night and over a dozen areas below freezing.
But temperatures are expected to be around average this week, with highs of 17 or 18C, the meteorologist added.
Autumn leaves will be even more spectacular this year
Sunnier summers have led to trees producing more sugar in their leaves this year, which will lead to more vivid and eye-catching colours, according to experts at Forestry England.
The picturesque autumn leaves can be spotted from mid-September to November in some parts of the UK.
As the days gradually get darker, the lack of sunlight reduces a plant’s production of chlorophyll – the chemical responsible for giving leaves a green pigment – which allows the beautiful yellow and orange shades, previously masked by the chlorophyll, to show through.
Some trees will also turn a vibrant red – the result of anthocyanin production, which is greater in years such as this one, when hot summers have increased the concentration of sugar in tree sap.
This triggers the tree to release anthocyanins as it tries to salvage the last of the energy from its leaves in preparation for winter.
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