Autumn Arrives with the Fall Equinox on September 22

Solstices and Equinoxes. Diagram courtesy of https://astro4edu.org/resources/diagram/bA48h020s763/

As summer begins to wind down and the days gradually grow shorter, the official start of astronomical fall is approaching. This year, the autumnal equinox will occur on Tuesday, September 22, 2026, at 8:05 p.m. EDT, marking the beginning of fall in the Northern Hemisphere.

The autumnal equinox, also known as the fall or September equinox, occurs at the precise moment the Sun crosses the celestial equator while moving south. At this point in Earth's annual journey around the Sun, neither hemisphere is tilted significantly toward or away from the Sun. After the equinox, those of us in the Northern Hemisphere will experience increasingly longer nights and shorter days until the winter solstice on December 21.

The word equinox comes from the Latin words aequus, meaning "equal," and nox, meaning "night." Despite the name, however, day and night are not exactly 12 hours long on the equinox. Because Earth's atmosphere bends sunlight and because sunrise and sunset are measured using the edge of the Sun rather than its center, there are actually a few extra minutes of daylight. The date when daylight and darkness are closest to equal is known as the "equilux," which will occur in most of the continental United States a few days after the equinox.

Earth's 23.4-degree tilt is responsible for our changing seasons. During summer, the Northern Hemisphere is tilted toward the Sun, bringing longer days. By winter, it is tilted away, resulting in shorter days. During the spring and fall equinoxes, Earth's position creates a temporary balance between the two. Around the equinox, the Sun also rises essentially due east and sets due west across most of the world.

The changing season will soon become increasingly visible. Birds begin their journeys south, temperatures cool, animals prepare for colder weather and leaves begin changing from summer greens to the familiar reds, oranges and yellows of autumn. Daylight has already been decreasing since the summer solstice in June and will continue to decline until the winter solstice in December.

Fall has also traditionally been associated with the harvest. The full Moon closest to the autumnal equinox is known as the Harvest Moon. In 2026, it will occur on Friday, September 25, just three nights after the equinox. The name dates to a time when farmers took advantage of the bright moonlight and relatively short period between successive moonrises to continue bringing in crops after sunset.

Cultures around the world have developed traditions surrounding the arrival of autumn and the harvest season. These range from Mabon harvest celebrations to Japan's Buddhist Higan observance and gatherings at Mexico's Chichen Itza, where the angle of the equinox Sun creates a famous pattern of light and shadow along the pyramid of El Castillo.

There are actually two ways of determining when fall begins. Meteorologists consider September 1 the beginning of fall and divide the seasons into three-month periods for weather and climate recordkeeping. Astronomical fall, however, is determined by Earth's position relative to the Sun and begins with the autumnal equinox.

So, whether your favorite part of fall is cooler weather, colorful leaves, pumpkins, football or simply spending an evening outside without the summer heat, mark September 22 on your calendar. At 8:05 p.m., summer officially gives way to autumn, beginning the seasonal journey toward the shorter, colder days of winter.

Information for this article was drawn from the Farmers' Almanac guide to the 2026 fall equinox. (https://www.farmersalmanac.com/fall-equinox-first-day-of-fall)