For most people, the official start of autumn is the . This is the moment when the sun crosses the celestial equator, making day and night nearly equal in length. Northern Hemisphere: Usually occurs on September 22 or 23 . Southern Hemisphere: Usually occurs on March 20 or 21 .
In the Northern Hemisphere, autumn typically begins around and ends around December 21 or 22 . This period is also known as fall. when is autumn
Autumn is an important season for many reasons: For most people, the official start of autumn is the
| Hemisphere | Meteorological Start | Astronomical Start (Equinox) | Typical Months | | :--- | :--- | :--- | :--- | | | September 1 | September 22–24 | September, October, November | | Southern | March 1 | March 19–21 | March, April, May | Southern Hemisphere: Usually occurs on March 20 or 21
Understanding when autumn starts helps with everything from agriculture to energy management. Farmers use these dates to time their final harvests, while city planners use them to prepare for increased heating demands and leaf clearance.
This definition is much easier for record-keeping and forecasting because the dates never change, regardless of the Earth's tilt or orbit. 3. Phenological Autumn (The Nature approach)