09/22/2025
First Day of Fall
The fall equinox and the first day of autumn arrive today: Monday, September 22, 2025, at 2:19 P.M. EDT in the Northern Hemisphere. The autumnal equinox is an astronomical event that marks the start of autumn (or fall). In the Northern Hemisphere, the autumnal equinox occurs in September; in the Southern Hemisphere, it occurs in March. For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier.
For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier.
For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier.
For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier.
For those in the Northern Hemisphere, when the Sun crosses the equator going from north to south, this marks the autumnal equinox; when it crosses from south to north, this marks the vernal equinox. In the Southern Hemisphere, it’s the reverse.
After the autumnal equinox, days become shorter than nights as the Sun continues to rise later and nightfall arrives earlier.
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.
Fall’s fiery colors are one of nature’s most stunning shows, but did you know those brilliant reds, oranges, and yellows were hiding all summer long? It’s true! The vibrant hues you see when the leaves change aren’t just about chilly weather—they’re all about sunlight, chemistry, and clever trees getting ready for winter. Let’s dive into the fascinating science behind why leaves change color and how weather and tree types create the perfect autumn masterpiece.
Why Do Trees Change Color?
Nature is so fascinating! The main reason for the eye-popping color change is not autumn’s chilly weather but sunlight—or rather, the lack of daylight. Day and night are roughly equal in length on the autumnal equinox in late September, but afterward, nights are growing longer and days shorter.
As the autumn days shrink, the reduced daylight tells deciduous plants that it’s time to stop gathering energy and get ready for the dormant season—winter.
Ancient Autumn Equinox Celebrations Around the World
The fall equinox has been a day of celebration for cultures since ancient days, when people tracked the transitions of Earth’s journeys around the Sun.
• At Machu Picchu in Peru, an ancient stone monument called Intihuatana—meaning “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 Chichén Itzá. On the equinoxes, the light looks like a snake slithering down the pyramid’s steps.
• In England, Stonehenge was also built with the equinoxes and solstices in mind.
Catherine Boeckmann
Executive Digital Editor and Master Gardener
The Old Farmer’s Almanac
GetYourGuidetoGeorgia.com for your window into Georgia celebrations of the wonder of Fall.
