Autumnal Equinox 2021: The First Day of Fall

Facts & Folklore About the Fall Equinox

September 16, 2021
Autumn in Colorado

In 2021, the autumnal equinox—also called the September equinox or fall equinox—arrives on Wednesday, 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 (192286)

When Is the Autumnal Equinox?

The fall equinox arrives on Wednesday, September 22, 2021, at 3:20 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)
2021 Wednesday, September 22 Saturday, March 20
2022 Thursday, September 22 Sunday, March 20
2023 Friday, September 22 Monday, March 20
2024 Sunday, September 22 Tuesday, March 19

What Is the Autumnal Equinox?

Autumn days come quickly, like the running of a hound on the moor.
Irish proverb

The autumnal equinox—also called the September or fall equinox—is the astronomical start of the fall season in the Northern Hemisphere and of the spring season in the Southern Hemisphere.

What Is an Equinox?

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.)

During the 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. When the Sun crosses the equator from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox.

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

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!

An Astronomical Moon Name

The Harvest Moon is one of only two Moon names that are astronomical terms and aren’t tied to one specific month. Because it’s always the full Moon nearest to the equinox that’s called the “Harvest Moon,” either September or October’s full Moon can take on the name. (The other astronomical Moon name is the Hunter’s Moon, which is the full Moon that directly follows the Harvest Moon. It can occur in either October or November.)

This year, the Harvest Moon happens on Monday, September 20—just two days prior to the autumnal equinox. Read more about September’s Harvest Moon here!

Harvest moon with people standing in front

Fall Weather

It is the summer’s great last heat,
It is the fall’s first chill: They meet.

–Sarah Morgan Bryan Piatt

Another definition of fall is “nights of below-freezing temperatures combined with days of temperatures below 70 degrees Fahrenheit (21°C)”. From here on out, the temperatures begin to drop.

Find 12 months of long-range weather predictions in the new Old Farmer’s Almanac!

Fall Foliage

Note that fall foliage isn’t due to current weather conditions. This is a common misconception. Leaves change color because of the amount of daylight and photosynthesis. Learn more about autumn leaves.

Japanese maple leaf in fall

Fall Equinox FAQs

Q: Are Day and Night Perfectly Equal on the Equinox?

A:  Some say that during an equinox, day and night is equal. Well, not exactly. It depends on where you live.

On the equinox, the center of the Sun is indeed above the horizon for 12 hours. However, “sunrise” is said to begin when the upper edge of the Sun’s disk becomes visible above the horizon (which happens a bit before the center rises) and ends when the entire Sun has set. In this case, daylight is still a bit longer than nighttime. 

Not only that, but the Sun is actually visible when it is below the horizon, as Earth’s atmosphere refracts the Sun’s rays and bends them in an arc over the horizon. Yes, you can see the Sun before the edge actually reaches the horizon! This causes daylight to be longer than 12 hours as well.

However, they are very close to equal (the total lengths may differ by only a few minutes). 

Did you know our rise/set tool now provides day length? In Dublin, New Hampshire, USA—home of The Old Farmer’s Almanac—our day length on the equinox is 12:08 hours.

See our Sunrise/set calculator for day length in YOUR area.

Q: Is the Autumnal Equinox Really the First Day of Fall?

A: Based on the astronomical definition of seasons, yes, the autumnal equinox does mark the first day of fall (in the Northern Hemisphere). However, according to the meteorological definition of seasons, which is based on temperature cycles and the Gregorian calendar, the first day of fall is September 1.

Q: Can You Balance An Egg On the Equinox?

A: There’s an old-wife’s tale that you can stand an egg on its end of the equinox. Well, yes, it’s true (and fun to try). But it’s not only on the equinox. See more about equinox facts from Almanac astronomer, Bob Berman.

autumn woods

Signs of Fall

What are your local signs of fall? In many regions of the Northern Hemisphere, the landscape silently explodes with vibrant colors of red, yellow, and orange. The leaves begin to drop off the trees, providing endless hours of jumping into leaf piles for kids and raking them back up for parents!

Trees snapping and cracking in the autumn indicate dry weather.

Fall also brings some wonderful holidays, including Halloween and Thanksgiving, which carry us through the season until temperatures begin to drop, nights begin to get longer, and all the woodland critters start storing up for the long haul of winter

And don’t forget about the end of Daylight Saving Time, when we “fall” back, setting our clocks back one hour and regaining an hour of precious sleep!

Plants and trees are slowing down, as sunlight decreases, to get ready for the colder season ahead. In the garden, asters and chrysanthemums bloom beautifully as orange pumpkins and corn mazes abound.

Football season is warming up and so is sweater weather.

Also notice the arc of the Sun across the sky each day as it starts shifting south. Birds and butterflies migrate along with the path of our Sun!

Of course, you can you can easily notice the later dawns and earlier sunsets. See our sunrise/set tool for your area!

Purple Aster
Aster flowers

Ancient Autumn Traditions 

The fall equinox has been a day of celebration for cultures since ancient days. People tracked the transitions of the Earth’s journeys around the Sun.

  • At Machu Picchu in Peru, an ancient stone monument called Intihuatana—which means “Hitching Post of the Sun”—serves as a solar clock to mark the dates of the equinoxes and solstices.  
  • In Mexico, the Mayans built a giant pyramid called Chichen Itza. On the equinoxes, it looks as if a snake made of light slithers down the pyramid’s steps.
  • In England, Stonehenge was also built with the equinoxes and solstices in mind.

See Five Ancient Sites Aligned With the Equinoxes and Solstices.

Enjoy Autumn!

Wishing a colorful, cool, cozy autumn to all our Almanac readers. Tell us your favorite things about the fall season below!

To learn more about all four seasons and see when they begin, see First Day of Seasons.


Reader Comments

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My grandson and I always split a persimmon seed to see what kind of winter weather it predicts— knife, spoon, or fork.

Autumn Article

Greetings from Ireland! We have now entered the season of Autumn, in America/Canada it's called 'Fall'. I love this time of year, the tree's are beautiful & we have Halloween to look forward to, my favourite time of year. I love reading your articles, they are informative & fun. Best wishes.

What I like about Autumn

I enjoy the smell of the leaves as they fall and dry underneath my feet, and the coolness of the wind

Autumn traditions

My grandson and I always split a persimmon seed to see what kind of winter weather it predicts— knife, spoon, or fork.

Less daylight

The article mentions that after the autumnal equinox the sun rises later and sets earlier…but doesn’t this actually start happening after the Summer Solstice?


The Editors's picture

Yes, that’s right! We’ve edited the article to make that more clear.

This was a very good article

This was a very good article to read. I was looking for rituals to do for the autumnal equinox, and came across this interesting piece. Thank You!!

My favorite thing about Fall

My birthdate falls near the autumn equinox so I have always considered myself a 'fall girl'. One of my favorite traditions is going for a long drive through the beautiful mountains of North Carolina and happening on a farm stand decorated with cornstalks and pumpkins. Bonus if there is a scarecrow! Double bonus if the farmstead has caramel apples!

I enjoy all the seasons

I love living in a part of the country that we get all 4 seasons!! I'm not looking forward to to Summer ending it always goes so fast but Winter drags! Anyhow at least where I live the warmth will still linger around until late September /early October

Beautiful Fall Season

Many Blessings of Fall! Chincoteague Beach, weather cooling, fishing birds change of colors, walks along our beach, reflections of trees and flowers change, but Kindness stays the same! Ukulele HollyBloe

Fall couldn't get here sooner.

We're in the beginning of summer, I can't stand the summer heat. If I can between Memorial Day and Labor Day I'd stayed in the North or South Poles where its always cold. Love the fall and winter seasons.

Autumn’s around the corner!

Please don’t remind us! Almost the end of June and we’ve yet to see summer! I know some in our country are beginning unbearable and unimaginable heatwaves, but please don’t forget those of us who are still awaiting summer sunshine and warmth!


I enjoy the cooler weather & look forward to Fall each year. It's my favorite season. I look forward to cozy nights and holidays spent with family and friends.

Enjoying this beautiful weather

The mornings here in rural southern New Jersey have been absolutely beautiful. We are surrounded by the Pine barrens national reserve and many farms. We already see Canadian geese departing along with other migrating fowl, much earlier than last 2 years. Looks like a colder winter is in play.

Autumn.....or summer ?

This Autumn will start with 80 degrees come late afternoon here in SE Minnesota.
A nice way to start but many in this area will say, " To warm for this time of year "
Happy Fall, to All !

Jalali calendar is a solar calendar

The Jalali calendar is a solar calendar, Because months were computed based on precise times of solar transit between zodiacal regions, seasonal drift never exceeded one day, and also there was no need for a leap year in the Jalali calendar. However, this calendar was very difficult to compute; it required full ephemeris computations and actual observations to determine the apparent movement of the Sun. Some claim that simplifications introduced in the intervening years may have introduced a system with eight leap days in every cycle of 33 years. (Different rules, such as the 2820-year cycle, have also been accredited to Khayyam). However, the original Jalali calendar based on observations (or predictions) of solar transit would not have needed either leap years or seasonal adjustments.

Fall or Autumn? Why are there two words for the same season?

In the next few days, we will enter from Summer into a season that Americans commonly call "Fall," but also called "Autumn." Why there are two words for the same season, while other seasons are known by one name? And what is the history behind both of these words?

Fall and Autumn meaning

The Editors's picture

That is a very interesting question! Autumn is considered the more formal name and the older word from the Latin word “autumnus.” 

“Fall” is really more of an American word, interestingly enough, and not used universally in the same way in Britsh English.  Perhaps it’s because the Colonial New England region experiences the “fall of the leaves,” which is less common in England.

As autumn can get lumped into the autumn harvest time (which can have a broad range), fall is really more about that season in which this fall of the leaves takes place. 

Cas Blank's post of Sept. 10/20

I can just imagine the fruit trees so heavily laden. Very nicely written article - an apt description of autumn for sure. Thank you.

The Colouring of Autumn

Here, in Southern Alberta (Lethbridge County), autumn is approaching.....The fields of grain have been clipped short leaving a yellow-brown stubble like a man's new beard. The upright green lush plants have taken on a droopy look.....which means the sugar beets are waiting for the harvest. The trees, oak, still stand proud and uplifted, still reaching towards the sky but their green glossy heads are slowly turning orangey-gold as an old man that has started to turn grayish white. The grasses in the lawns are perking up now that a rain storm or two has past through the area. Apples, bowing down on slender branches, red and gold striped, are calling out to the gardener, "Come! Help me with my load!" The dark red plums are calling too, "We did this for you! Come pick and make a platz, a pie, anything......the burden is so great!" The Pears cry out, " Not yet! We need more time....we are green, not sweet....we need some frost to purify!" Finally, the maple trees say, "Ha! We can carry the colours through, because we are green, gold and red...... we are colours of autumn!" And, so, once again the garden, the fields, the orchard, and the lawns sing together while robins, sparrows, chickadee flit and fly southward. C.B.

Ready for Fall

Here in central Maryland, it is still very humid and summery. As an October baby, autumn is my favorite season!

Mosquitoes will soon stop chasing me around the garden. We can enjoy the colorful leaves, pumpkins, apples and warm drinks. Time for flannels, corduroy and sweaters pretty soon.

Had enough Summer before it started.

Sometimes I really envy some animals ability to hibernate. Wish I could have went to sleep around May and woke up around October, as that is how long summer seems to last in Texas. Still, the changes in daylight are becoming more apparent and the end of humid 95+ F days are in sight.

Permission to use pictures

Your pictures are beautiful. May I use some of your pictures for illustration in my book on forest ecology. I have not determined which ones I will use. I will write the proper citation regarding the source of the pictures. This book is for education purposes, not for commercial ones. Thank you very much. Sincerely, Wiryono.

Fall Equinox

I was able to stand two eggs this morning (3:43am)
Which makes 20 years that I have been standing eggs on the equinox
Bogus science and mythology in celebration of the season!

Fall Equinox

Autumn like the other seasons, I feel, reach their apex on the day that most people feel they start. Its a transitional thing where one gradually melds into the next. Its not so distinctive. There needs to be a rethink about this .

In Vancouver Washington we have noticed leaves changing to fall color and starting to drop for the past 2 weeks even though we are still having summer temps during the day. Come on Fall! We miss you!
In Vancouver Washington we have noticed leaves changing to fall color and starting to drop for the past 2 weeks even though we are still having summer temps during the day. Come on Fall! We miss you!In Vancouver Washington we have noticed leaves changing to fall color and starting to drop for the past 2 weeks even though we are still having summer temps during the day. Come on Fall! We miss you!


Autumn shows her lovely face in August. The light starts a noticeable change. Shadows are getting longer, the angle of the sun changes. My dogwood starts to change to red. Not many berries this year. The huge oaks across the street are producing acorns this year. They are immature, green and small, but last year there were none.
I love this time of year. The air is fresh, the heat is waning, the earth starts to glow with color along with the skies at dawn and sunset. Love the autumn foods, love the sweaters, boots, socks, and corduroys. Happiness and contentment.


Diane, your comment was so poetic and lovely. Thank you for it.


Diane, your comment was beautiful. Truly enjoyed reading it.


In Vancouver Washington we have noticed leaves changing to fall color and starting to drop for the past 2 weeks even though we are still having summer temps during the day. Come on Fall! We miss you!