Archive · 1 Sep 2025
Autumn's Start: Meteorological, Astronomical, and Phenological Definitions
Autumn's arrival isn't as simple as it seems!
There are a few ways to say when it starts.
The most common is based on the calendar, starting September 1st.
Another is when the sun and night are the same length, around late September.
A third way is when nature shows it's fall, like leaves changing color.
Climate change is mixing things up, sometimes causing 'false autumns' early, due to hot summers.
Overall, autumn is starting later and spring earlier due to global warming.
The UK is experiencing a 'false autumn' with early signs of the season.
Meteorological autumn begins on September 1st.
Astronomical autumn's start varies between September 21 and 24.
Phenological autumn start depends on natural events like leaf changes.
Climate change is shifting the timing of seasons.
- Who
- Met Office, Jadu Dash (professor)
- What
- The definition of autumn and its changing timing.
- When
- Meteorological autumn begins September 1st, astronomical around September 21-24
- Where
- UK, Northern Hemisphere
- Why
- To understand the start of autumn and the impact of climate change.
- Meteorological Autumn Start
- September 1st
- Astronomical Autumn Start (approx.)
- September 21-24
- Phenological Autumn Start
- Varies by year
- False Autumn Cause
- Stress from extreme summer conditions
- Climate Change Effect
- Autumn arriving later, spring earlier