When is the First Day of Fall?
The autumnal equinox, also known as the September or fall equinox, arrives on Sunday, September 22, 2024, at 8:44 A.M. EDT in the Northern Hemisphere. This event marks the official start of autumn and happens simultaneously around the world.
The equinox is an astronomical event that signals the beginning of fall in the Northern Hemisphere (in the Southern Hemisphere, it marks the start of spring in March). During an equinox, the Sun crosses the celestial equator—an imaginary extension of Earth’s equator into space. The autumnal equinox occurs when the Sun moves from north to south across this line, while the spring equinox happens when the Sun moves from south to north. In the Southern Hemisphere, these directions are reversed.
After the fall equinox, days become shorter than nights as the Sun rises later and sets earlier, leading up to the winter solstice when days will begin to lengthen again.
The term “equinox” comes from the Latin words “aequus,” meaning “equal,” and “nox,” meaning “night.” On this day, day and night are nearly equal in length.
The full Moon closest to the autumnal equinox is known as the Harvest Moon. This name comes from its significance in farming, as the full Moon rises around sunset for several consecutive nights, providing extra light for farmers to complete their harvests before the first hard frosts of fall. Typically, the Moon rises about an hour later each night, but during the fall equinox, it rises only about 20 to 30 minutes later, making it appear almost as if it’s rising at the same time each night.
The Harvest Moon is one of two Moon names that are tied to astronomical events rather than a specific month. The other is the Hunter’s Moon, which follows the Harvest Moon and can occur in either October or November.
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