When Does Autumn Start – UK and US Dates for 2025 and 2026
For anyone in the UK or the USA wondering when autumn starts, the answer is not as straightforward as a single date on the calendar. The season officially begins on two different days, depending on whether one follows the astronomical or the meteorological definition. Both systems are widely used, but they serve different purposes, and knowing the distinction helps make sense of conflicting dates found online.
In the UK, the start of autumn can fall on 1 September (the meteorological version) or around 22–23 September (the astronomical version, marked by the autumnal equinox). The USA follows the same two systems, though the season is commonly referred to as “fall.” This article lays out the exact dates for 2025 and 2026, explains why two definitions exist, and clarifies what applies in different regions.
When does autumn start in the UK?
1 September – 30 November
22 September – 21 December
22 or 23 September – 21 December
Same dates, but often colloquially “fall”
- Autumn has two official start dates because of different measurement systems: meteorological (fixed by months) and astronomical (based on Earth’s orbit).
- The astronomical equinox varies between 22 and 23 September (occasionally 21 or 24) due to calendar drift and leap years.
- In the UK, meteorological autumn is used by weather services such as the Met Office for consistent record-keeping; astronomical autumn aligns with traditional equinox observations.
- For 2025, the autumnal equinox falls on 22 September at 19:19 UTC, marking the astronomical start.
- Users near London or Manchester follow the same UK dates – no regional variation exists within the country.
| Type | Start Date | End Date | Based On |
|---|---|---|---|
| Meteorological | 1 September | 30 November | Calendar months (temperature) |
| Astronomical (2025) | 22 September | 21 December | Earth’s orbit / equinox |
| Astronomical (2026) | 22 or 23 September | 21 December | Earth’s orbit / equinox |
| Solar (Celtic) | 1 August | 31 October | Traditional / calendar |
What is the difference between meteorological and astronomical autumn?
The core difference lies in what each system uses to define the season. Meteorological autumn relies on fixed calendar months, while astronomical autumn follows the position of Earth relative to the Sun.
Meteorological autumn: fixed by temperature and calendar
The meteorological system divides the year into four three-month seasons based on the annual temperature cycle. Autumn is defined as September, October, and November in the Northern Hemisphere. This approach, adopted by meteorologists and climatologists, makes it easier to compare seasonal statistics from year to year. The Met Office uses this definition for all its weather data and forecasting.
Astronomical autumn: based on Earth’s orbit and equinox
Astronomical autumn starts at the autumnal equinox, the moment when the Sun crosses the celestial equator, making day and night nearly equal in length. In the Northern Hemisphere, this occurs around 22 or 23 September. The season then lasts until the winter solstice in December. The National Physical Laboratory and the Royal Museums Greenwich provide precise timing for these events each year.
The dual definition arises from different needs. Meteorological seasons give climate scientists consistent 90-day blocks for analysis. Astronomical seasons reflect the traditional calendar tied to solstices and equinoxes, which has been used for centuries in farming, culture, and astronomy. Neither is more correct; they simply serve different purposes.
Key dates for meteorological and astronomical autumn
For 2025, the astronomical equinox occurs on 22 September, according to the US National Weather Service. For 2026, preliminary data from the Royal Museums Greenwich places the equinox on 23 September at 12:06 AM GMT. Meteorological autumn, by contrast, always begins on 1 September regardless of the year.
When does autumn start and end?
Meteorological autumn: September 1 to November 30
Under the meteorological system, autumn covers exactly three calendar months. This applies uniformly across the UK and the USA. The dates never shift, making them reliable for planning and data collection. The Countryfile guide confirms this fixed schedule for both countries.
Astronomical autumn: equinox to winter solstice
Astronomical autumn runs from the autumnal equinox to the winter solstice (around 21 December). Its length varies slightly because Earth’s orbit is elliptical. In 2025, the season lasts from 22 September to 21 December. In 2026, it starts on 22 or 23 September and ends on 21 December.
Autumn duration in different hemispheres
In the Northern Hemisphere, autumn spans September through December under the astronomical system. In the Southern Hemisphere, the seasons are reversed: autumn runs from March to June. This article focuses on the UK and USA, both in the Northern Hemisphere.
When does autumn start in the USA?
Meteorological fall in the US (1 September)
The US National Weather Service uses meteorological fall, which begins on 1 September and ends on 30 November. This system is standard across all US climate reports and aligns with the UK approach.
Astronomical fall in the US (autumnal equinox)
Astronomical fall in the USA starts at the same autumnal equinox as in the UK. For 2025, the equinox occurs on 22 September at 6:19 PM EDT, per the NWS. The term “fall” is used interchangeably with “autumn” across the country. For a deeper look at the equinox itself, see our guide on What is the autumnal equinox?.
Whether you call it autumn or fall, the meteorological start is always 1 September. If you see a date around 22 or 23 September mentioned in news articles or almanacs, that refers to the astronomical equinox. Both are correct in context.
Regional variations in fall start dates
No official regional variation exists within the USA for either definition. However, phenological signs such as leaf colour change can vary significantly by latitude and local climate. These natural indicators often align more closely with astronomical autumn, as noted by phenology projects tracking seasonal changes.
When does autumn start in 2026?
- Ancient times – The Celtic calendar marked the start of autumn at Lughnasadh (1 August), based on solar and agricultural cycles.
- 19th century – Meteorological seasons were introduced by climatologists to create consistent data records across years.
- 2022 – Astronomical autumn began on 22 September; meteorological autumn on 1 September.
- 2025 – Astronomical autumn: 22 September. Meteorological autumn: 1 September.
- 2026 – Astronomical autumn: 22 or 23 September (exact date depends on UTC timing). Meteorological autumn: 1 September.
For 2026, the Calendarr reference confirms the equinox will fall on 22 or 23 September, with the exact time to be confirmed by astronomical almanacs closer to the date.
Is autumn starting on September 1 or the equinox?
| Established information | Information that remains unclear |
|---|---|
| Meteorological autumn always starts on 1 September. No variation. | The exact date of the autumnal equinox for a given year can shift by one day depending on UTC timing and leap-year adjustments. |
| Dates are consistent across the entire UK and most UK cities. The USA follows the same astronomical equinox. | For 2026, preliminary predictions suggest 22 or 23 September, but the exact date will be confirmed only when official astronomical calculations are finalised. |
| Many people assume autumn starts on 1 September (meteorological), while others look to the equinox. Both are correct in different contexts. | Climate change may affect phenological indicators of autumn (e.g., leaf fall timing), but calendar dates remain unchanged. |
Why does autumn have two start dates?
The dual definition of autumn arises from the need for consistent climate data (meteorological) versus cultural and astronomical tradition. In the UK, the Met Office officially uses meteorological seasons for weather statistics, while astronomical seasons are tied to equinoxes and solstices. The Woodland Trust’s Nature’s Calendar project tracks phenological signs such as leaf colour, which align more closely with astronomical autumn. No single “correct” answer exists; the best answer depends on whether one needs fixed calendar planning or astronomical event tracking.
Which sources define autumn start dates?
“Autumn starts in September and finishes in November – meteorological definition.”
– Met Office
“The seasons are defined as spring (March, April, May), summer (June, July, August), autumn (September, October, November) and winter (December, January, February).”
– Woodland Trust
“The other answer is astronomical autumn, which starts at the autumn equinox – usually on 22 or 23 September.”
– BBC Newsround
The Woodland Trust and BBC Newsround provide accessible explanations for general audiences, while the Wikipedia entry offers a comprehensive overview of both definitions and their global variations.
So when does autumn actually begin?
The answer depends on which system you choose. For everyday planning and weather reports, meteorological autumn starting on 1 September is the default in both the UK and USA. For those who follow astronomical events or traditional calendar markers, the autumnal equinox around 22 or 23 September signals the true start. Neither definition is wrong. Learn more about the exact mechanisms behind the seasonal shift by reading What is the autumnal equinox?.
Frequently asked questions about autumn start dates
When does autumn start near London?
The same as the rest of the UK: meteorological autumn starts 1 September; astronomical autumn starts around 22–23 September.
When does autumn start near Manchester?
Same as London – no regional variation within the UK.
When does autumn start in the USA?
Meteorological fall starts 1 September; astronomical fall starts at the autumnal equinox (same date as UK). The season is often called “fall” in the US.
When does autumn start in 2022?
Astronomical autumn started on 22 September 2022; meteorological autumn started on 1 September 2022.
When does autumn start in the UK in 2026?
Meteorological autumn starts 1 September 2026. Astronomical autumn will be on 22 or 23 September 2026 (exact date to be confirmed).
When is mid-autumn?
Mid-autumn is around 15 October in the UK, marking the midpoint of meteorological autumn. The Mid-Autumn Festival in East Asia follows the lunar calendar, usually in late September or early October.
Is it autumn now in the UK?
Check the current date: if it is between 1 September and 30 November, it is meteorological autumn. For astronomical autumn, it runs between the equinox and the winter solstice.
When does autumn start in England?
Same as the rest of the UK: meteorological autumn on 1 September, astronomical autumn around 22–23 September.
What are the autumn months?
Meteorological autumn covers September, October, and November. Astronomical autumn spans from the autumnal equinox (September) to the winter solstice (December).
When does autumn begin?
Meteorological autumn begins on 1 September. Astronomical autumn begins on the autumnal equinox, usually 22 or 23 September.
More related posts
Jack Skellington – Biography, Movies, Costumes, and Fun Facts
Joe Pesci – Biography, Net Worth, Movies and Current Status
Diane Morgan Movie and TV Show – Full Filmography & Career Guide
Left Side Chest Pain – Causes, Red Flags and Action Steps
Speak No Evil 2024 – Plot, Cast, Release and Reviews
Cineworld Cinema – Warrington – Showtimes, Tickets and Location Guide
Jalen Brunson – Biography, Career and Key Facts
