Countdown to Fall

This countdown points to September 22, the most common date of the September equinox and the astronomical start of autumn in the Northern Hemisphere. (The exact moment shifts between September 21 and 23 depending on the year.)

Sweater weather, pumpkin everything, and the run-up to Halloween — fall fans start checking this page in July, and honestly, fair.

The September equinox marks the sun crossing the celestial equator heading south — astronomical autumn for the Northern Hemisphere. Harvest festivals have anchored to this moment across cultures, from Europe's harvest home feasts to East Asia's Mid-Autumn Festival season.

Like its March twin, the date drifts between September 21 and 23. This page uses September 22, the most common date, and the sweater-weather anticipation takes it from there.

Ask "how many days until fall?" and you can get two honest answers, because there are two ways to define the season.

Astronomical fall is based on where Earth is in its orbit. It begins at the September equinox, the moment the sun crosses the celestial equator heading south. That usually lands on September 22 or 23 (and occasionally September 21), which is why this countdown points to September 22. Astronomical fall runs until the December solstice, around December 21.

Meteorological fall is based on the calendar and the temperature cycle. Weather scientists split the year into four tidy three-month blocks so that seasonal records are easy to compare from year to year. In the Northern Hemisphere, meteorological fall is simply September, October, and November — it always starts on September 1 and ends on November 30.

So if your countdown hits zero on September 1, you are counting to meteorological fall. If it hits zero around September 22, you are counting to the equinox — the date most calendars print as the "first day of fall." Either way, the days until fall shrink fast once Labor Day passes.

The seasons are flipped south of the equator. While the Northern Hemisphere welcomes fall in September, places like Australia, New Zealand, South Africa, Argentina, and Chile are heading into spring.

In the Southern Hemisphere, astronomical fall (usually called autumn there) begins at the March equinox, around March 20, and lasts until the June solstice, around June 21. Meteorological autumn covers March, April, and May, starting on March 1 — and Australia uses that March 1 date as its official start of autumn.

If you are counting down to autumn in the Southern Hemisphere, our first day of spring countdown tracks the March equinox, the same moment that starts fall down south.

Astronomical fall in the Northern Hemisphere lasts roughly 90 days, from the September equinox to the December solstice. Meteorological fall lasts exactly 91 days every year: 30 days of September, 31 of October, and 30 of November.

Fall ends when winter begins. On the astronomical calendar that is the December solstice, the shortest day of the year — you can follow it with our first day of winter countdown. On the meteorological calendar, winter starts on December 1.

Along the way, fall packs in some of the most anticipated dates of the year: Halloween on October 31 and Thanksgiving on the fourth Thursday of November.

Fall and autumn mean exactly the same season. "Autumn" is the older word, coming into English from French and, before that, Latin. "Fall" grew out of the phrase "the fall of the leaf," which was shortened over time. Both words were used in England for centuries; "fall" became the everyday choice in American English, while "autumn" stayed more common in British English.

The word "equinox" comes from Latin for "equal night." On the equinox, day and night are close to the same length everywhere on Earth. They are not perfectly equal, though — the way sunlight bends in the atmosphere and the way sunrise and sunset are measured give most places a few extra minutes of daylight on the equinox itself. After the September equinox, nights in the Northern Hemisphere keep getting longer until the winter solstice.

The famous fall colors are a direct result of shorter days. During spring and summer, leaves are packed with green chlorophyll, which the tree uses to turn sunlight into food. As the days get shorter and cooler, trees slow down and stop making new chlorophyll, and the green fades.

• Yellows and oranges come from pigments called carotenoids. They were in the leaf all summer, hidden under the green.
• Reds and purples come from anthocyanins, which many trees, such as maples, produce in the fall. Sunny days and cool (but not freezing) nights tend to make the reds brighter.
• Browns appear as the leaf dries out and the other pigments break down.

Peak color arrives first in the far north and in the mountains, then moves south and downhill over several weeks. In much of the northern United States, the best leaf-peeping often lines up with late September through mid-October — right around the first weeks of fall.

The best part of counting the days until fall is planning what to do when it arrives. Here is a fall bucket list to get you started:

• Go apple picking and bake something with the haul.
• Visit a pumpkin patch and pick the perfect jack-o'-lantern pumpkin.
• Find your way through a corn maze.
• Take a scenic drive or hike to see the leaves change.
• Watch for the Harvest Moon, the full moon closest to the equinox.
• Make a pot of chili or soup on the first cool evening.
• Jump into a pile of raked leaves (any age counts).
• Start planning Halloween costumes and decorations.
• Have a bonfire or fire-pit night with s'mores.
• Pull out the sweaters, blankets, and the coziest socks you own.

Want more ideas? Our spooky season bucket list and Halloween family bucket list are great next stops, and the Thanksgiving countdown activities will carry you all the way through November.