Equal day and night? It can also happen in June!
According to the astronomical definition, fall begins with the autumnal equinox. In the Northern Hemisphere, it's the September equinox; south of the equator, it is the equinox in March.
Equinoxes and solstices in your city
North America, Europe, most of Asia, Northern Africa
In Toronto, Ontario, Canada: Monday, September 22, 2025 at 2:19 pm EDT
(Change location)
This corresponds to Monday, September 22, 2025 at 18:19 UTC.
Australia, New Zealand, South America, southern Africa
In Toronto, Ontario, Canada: Friday, March 20, 2026 at 10:46 am EDT
(Change location)
This corresponds to Friday, March 20, 2026 at 14:46 UTC.
Meteorologists use a different method of defining the first day of fall. In some countries, the beginning of the seasons is determined by average temperatures rather than fixed dates or astronomical events.
Meteorological and other seasons definitions
In most locations on Earth—except for tropical regions—the start of fall is accompanied by rapidly shortening days.
At any given location, the day-to-day difference in day length is greatest around the days of the equinoxes. After the fall equinox, days still get shorter, but at an ever-decreasing rate. On the shortest day of the year, the winter solstice, the day-to-day difference reaches zero.
Locations closer to the poles experience larger day-to-day differences:
Day-to-day differences in your city
Our Earth is tilted as it orbits the Sun, which is why we have seasons on Earth.
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Astronomical fall begins on the day of the equinox. The name derives from Latin and means equal night, giving the impression that both day and night are exactly 12 hours long. However, that is not entirely true. In most regions, the day of the equinox is a bit longer than 12 hours.
The date when day and night are actually equal is called the equilux. It falls a few days before the spring equinox and some days after the fall equinox in both hemispheres.
Other astronomical terms & definitions
In the temperate zone, fall is also when the warm, stable weather of summer gives way to colder, more erratic weather conditions. However, this varies substantially from one region to another.
Climate and monthly average temperatures in your city
The start of autumn and the fall equinox are celebrated in cultures and religions around the world with various fall traditions, holidays, and festivals.
Fall festivals: Mabon, Navaratri, and the Snake of Light
Navaratri is a Hindu autumn festival dedicated to the goddess Durga.
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In the Northern Hemisphere, astronomical and meteorological autumn runs from September to December. South of the equator, it starts in March and ends in June. Read more about the history and meaning of the fall months:
September | October | November | December
Earth does not move at a constant speed in its elliptical (oval) orbit. This means the seasons are not equal in length. On average, fall lasts 89.8 days in the Northern Hemisphere and 92.8 days in the Southern Hemisphere.
Average season lengths:
Both fall and autumn are correct English terms for the season preceding winter. Autumn is primarily used in British English, while fall is a term more frequently used in American English.