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When Is the First Day of Fall 2021?

North of the equator, fall begins in September; in the Southern Hemisphere, it starts in March. Find out exact dates and how the fall season is defined.

Illustration image

In temperate climes, fall can be magical as trees display their autumn foliage.

©iStockphoto.com/Songquan Deng

Fall 2021 Dates

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.

September Equinox 2021 (Autumn Equinox, Northern Hemisphere)

(North America, Europe, most of Asia, northern Africa)

March Equinox 2021 (Autumn Equinox, Southern Hemisphere)

(Australia, New Zealand, South America, southern Africa, part of Asia)

Alternative Fall Start Dates

Meteorologists use a different method of defining the first day of fall. And, in some countries, the beginning of the seasons is determined by average temperatures rather than fixed dates or astronomical events.

Dwindling Daylight

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.

At the same time, locations closer to the poles experience larger day-to-day differences. In Toronto, the day of the fall equinox is just under 3 minutes shorter than the previous day; in Miami, roughly 2000 kilometers or 1200 miles farther south, the difference is only about 1 minute and 30 seconds.

Equinox and solstice illustration.
Equinox and solstice illustration.

Our Earth is tilted as it orbits the Sun, which is the reason we have seasons on Earth.

Equal Day and Night?

Astronomical fall begins on the day of the equinox. The name of the event 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.

Falling Temperatures

In the temperate zone, in particular, fall is also the time when the warm, stable weather of summer gives way to colder, more erratic weather conditions, though this varies substantially from one region to another.

Traditions and Folklore

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 Months

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:

Northern fall months

September | October | November | December

Southern fall months

March | April | May | June

Fall or Autumn?

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.

Topics: Astronomy, Seasons, September, March, Equinox