Meteorologists divide seasons into neat, 3-month blocks for climate records.

The autumnal equinox, also known as the September equinox, is a significant event celebrated by cultures around the world. It marks the moment when the sun appears directly above the equator, and the day and night are equal in length. Many ancient civilizations, such as the ancient Greeks and Mayans, revered this day as a time of harvest and thanksgiving.

In conclusion, the start of autumn depends on the definition used. While meteorological autumn begins on September 1st in the Northern Hemisphere, the astronomical definition marks the beginning of the season on September 22nd or September 23rd. Regardless of the exact date, autumn is a season of transition, marked by the changing colors of the leaves, the cooling of the air, and the excitement of a new season.

(U.S., Europe, Canada, China): Autumn starts between September 21–24 .

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Note: If you live in the Southern Hemisphere (like in Australia or Brazil), these dates are flipped. Their autumn begins in March!

In the United States, the first day of autumn is often considered to be September 22nd or September 23rd, depending on the year. This date marks the official beginning of the season, and many people celebrate by enjoying the outdoors, apple picking, and sipping pumpkin spice lattes.

Deciduous trees stop producing chlorophyll, revealing vibrant reds, oranges, and yellows.

This method always starts autumn on the , making weather data comparison easier.

If you prefer your seasons dictated by the tilt of the Earth and the position of the sun, you follow the astronomical calendar. This is the date most people recognize as the "official" start of fall.

In the Northern Hemisphere, meteorological autumn begins on September 1st and ends on November 30th. This definition is based on the annual temperature cycle and the climatological patterns of the region. Meteorologists use this definition to make it easier to compare data from year to year.