First Day of Fall 2022: The Autumnal Equinox

What is the Autumnal Equinox?

Fall begins on September 22, early in the morning at 4:21 A.M. The autumnal equinox is when the Sun appears to cross the celestial equator from north to south. (The celestial equator is the circle in the celestial sphere halfway between the celestial poles. It can be thought of as the plane of Earth’s equator projected out onto the sphere.)

Another definition of fall is nights of below-freezing temperatures combined with days of temperatures below 70 degrees Fahrenheit.

The word equinox means “equal night”; night and day are about the same length of time. This occurs two times each year: Vernal in late March and Autumnal in late September.

In addition to the (approximately) equal hours of daylight and darkness, the equinoxes are times when the Sun’s apparent motion undergoes the most rapid change. Around the time of the equinoxes, variations in the position on the horizon where the Sun rises and sets can be noticed from one day to the next by alert observers.

From here on out, the temperatures begin to drop and the days start to get shorter than the nights.

In 2022, the autumnal equinox—also called the September equinox or fall equinox—arrives on Thursday, September 22. This date marks the start of fall in the Northern Hemisphere and spring in the Southern Hemisphere. Read about the signs of fall and the ways we mark the approaching equinox. 

Autumn has caught us in our summer wear.

–Philip Larkin, British poet (1922–86)

When Is the Autumnal Equinox?

The fall equinox arrives on Thursday, September 22, 2022, at 9:04 P.M. EDT in the Northern Hemisphere. The equinox occurs at the same moment worldwide.

Autumnal Equinox Dates

Year Autumnal Equinox (Northern Hemisphere) Autumnal Equinox (Southern Hemisphere)

2022 Thursday, September 22 Sunday, March 20
2023 Saturday, September 23 Monday, March 20
2024 Sunday, September 22 Tuesday, March 19
2025 Monday, September 22 Thursday, March 20

Note: Dates listed above are based on Eastern Time (UTC-5). Due to time zones, the date of the equinox may differ by +/- one calendar day in your location.

What Is the Autumnal Equinox?

The autumnal equinox is an astronomical event that marks the start of autumn (or “fall”). In the Northern Hemisphere, the autumnal equinox occurs in September; in the Southern Hemisphere, it occurs in March. 

What Is an Equinox?

During an equinox, the Sun crosses what we call the “celestial equator”—an imaginary extension of Earth’s equator line into space. The equinox occurs precisely when the Sun’s center passes through this line.

For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.

After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier. This ends with the winter solstice, after which days start to grow longer once again. 

The word “equinox” comes from Latin aequus, meaning “equal,” and nox, ”night.” On the equinox, day and night are roughly equal in length. (See more about this below.)

Fall bridge

The Harvest Moon & the Equinox

One of our favorite pieces of trivia surrounding the autumnal equinox involves its relationship with the full Moon. Curiously, the full Moon that occurs nearest to the autumnal equinox is always called the ”Harvest Moon!” Why is that?

Surprise, surprise: it has to do with farming! Around the fall equinox, the full Moon rises around sunset for several nights in a row, which traditionally provided farmers with just enough extra light for them to finish their harvests before the killing frosts of fall set in. Normally, the Moon rises about an hour later each night, but around the time of the fall equinox, the angle of the Moon’s orbit and the tilt of the Earth line up just right and cause the Moon to rise only about 20 to 30 minutes later each night for several nights in a row!

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