When is autumn 2025: Why season has two start and end dates

Sir Keir Starmer declared on Monday, September 1, that “summer is definitely over,” but, while many would disagree with much else the prime minister has said, this did strike a chord.

Debate ensued as to when autumn officially begins with some, like the PM, stating it comes with the beginning of the month - and others giving a date of Monday, September 22.

Unofficial metrics for measuring the beginning of autumn include:

• When pumpkin lattes go on sale (September 4 in 2025),
• When the school term begins,
• The political party conference season,
• The start of the UCI World Cycling Championships (September 21 in 2025)

Here is the official timeline of when autumn falls in 2025.

When does autumn begin in 2025?

There are in fact two dates - and you could maybe choose which one you prefer, if you want summer to last a little bit longer.

Astronomical autumn is dictated by the Earth's axis and orbit around the Sun. According to this, autumn begins on Monday, September 22 in 2025 and ends on Sunday, December 21, which is the shortest day of the year and the beginning of winter.

According to the Met Office: “The astronomical calendar determines the seasons due to the 23.5 degrees of tilt of the Earth's rotational axis in relation to its orbit around the Sun.

“Both equinoxes and solstices are related to the Earth's orbit around the Sun.”

Meteorological seasons are derived by splitting the year into four periods made up of three months each, the Met Office states, and this is easier to work out by equal three-month periods.

Autumn is defined by the meteorological calendar as being September 1 to November 30.

The Met Office states: “These seasons are split to coincide with our Gregorian calendar, making it easier for meteorological observing and forecasting to compare seasonal and monthly statistics.”