Fall Facts and Trivia: 12 Things to Know About the Autumnal Equinox and Harvest Season

Fall is officially arriving in the Northern Hemisphere, bringing shorter days, longer nights, cooler temperatures and the beginning of the autumn season. But the autumnal equinox is more than changing leaves and pumpkin spice.

The 2026 autumnal equinox occurs on Sept. 23 at 00:05 UTC, although it falls on Sept. 22 in parts of North America because of time-zone differences. The event marks the astronomical beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. From the meaning of the word “equinox” to the reason the Harvest Moon is linked to farming, here are 12 fall facts and pieces of trivia to know as the season begins.

1. The Autumnal Equinox Marks the Start of Astronomical Fall

The autumnal equinox is the point when the centre of the Sun crosses Earth’s equatorial plane from north to south. In the Northern Hemisphere, this marks the beginning of astronomical fall. South of the equator, the same event marks the beginning of spring.

In 2026, the September equinox occurs at 00:05 UTC on Sept. 23. In New York, for example, that corresponds to 8:05 p.m. EDT on Sept. 22.

2. “Equinox” Means “Equal Night”

The word equinox comes from the Latin words aequus, meaning “equal”, and *nox”, meaning “night.”

The name refers to the idea that day and night are approximately equal in length around the equinox. However, they are not actually exactly 12 hours each in most locations because of atmospheric refraction and the way sunrise and sunset are defined.

3. Fall Does Not Start on the Same Date Everywhere

The autumnal equinox usually occurs on Sept. 22 or 23, but the exact date and local time can vary. There are also two different ways of defining the seasons. Astronomical fall begins with the September equinox, while meteorological fall is defined as September, October and November in the Northern Hemisphere.

4. Earth’s Tilt Causes the Seasons

Earth’s axis is tilted as the planet travels around the Sun. That tilt changes the amount and angle of sunlight reaching different parts of the planet throughout the year.

At the September equinox, neither hemisphere is tilted towards the Sun, and the Sun is directly above Earth’s equator. After the equinox, the Northern Hemisphere continues moving towards shorter days and longer nights.

5. Days Start Getting Shorter in the Northern Hemisphere

Once the autumnal equinox passes, daylight continues to decrease across the Northern Hemisphere as the region heads towards the winter solstice. The Sun’s apparent path across the sky becomes shorter, meaning less daylight and increasingly longer nights.

The opposite happens in the Southern Hemisphere, where daylight hours increase as spring progresses.

6. The Harvest Moon Arrives Close to the Equinox

The Harvest Moon is the Full Moon closest to the autumnal equinox. In 2026, the Harvest Moon reaches its full phase on Sept. 26. NASA says it will rise near Saturn and Neptune, creating a notable skywatching opportunity.

7. The Harvest Moon Helped Farmers Work After Sunset

The Harvest Moon gets its name from its historical connection to the agricultural harvest. Around the September equinox, the Moon can rise only a relatively short time later on successive evenings in the Northern Hemisphere. This meant farmers historically had additional natural light after sunset during the harvest period, allowing them to continue working later into the evening.

8. The Harvest Moon Is Not Always Orange

Despite the familiar images of a huge orange or reddish Harvest Moon, the Moon itself does not suddenly change colour because it is the Harvest Moon. A low Moon can appear yellow, orange or reddish because its light passes through more of Earth’s atmosphere when it is close to the horizon. The effect can be particularly noticeable during moonrise.

9. The September Equinox Happens Twice a Year

There are two equinoxes every year: one in March and one in September. The March equinox marks the beginning of astronomical spring in the Northern Hemisphere, while the September equinox marks the beginning of astronomical autumn. The seasons are reversed in the Southern Hemisphere.

10. Fall Is Not Exactly the Same Length Every Year

The astronomical seasons do not all last exactly the same number of days. Earth takes about 365.24 days to orbit the Sun, and its orbit is not a perfect circle. As a result, the lengths of the astronomical seasons vary, generally ranging from about 89 to 93 days.

11. Autumn Is a Season of Major Changes in Nature

The changing amount of sunlight affects plants and animals as autumn progresses. In many parts of the Northern Hemisphere, trees respond to shorter days by reducing chlorophyll production. As the green pigment fades, other pigments become more visible, producing the yellow, orange and red colours associated with fall foliage.

The timing and intensity of autumn colours can vary depending on location, species and weather conditions.

12. Fall Begins Differently Depending on Which Hemisphere You Live In

For people in the Northern Hemisphere, the September equinox means autumn has arrived. But for people south of the equator, the same astronomical event marks the beginning of spring. In other words, while people in the US, Canada and much of Europe are preparing for fall, people in Australia, South Africa and parts of South America are moving into spring.