Fall doesn’t begin with just cooler weather and colorful leaves. It officially starts with the autumn equinox, which occurs on September 22, 2025. According to the Farmers’ Almanac, it begins at 2:19 p.m. (eastern time). This is when day and night are almost the same length.
What Is the Autumn Equinox?
The word “equinox” comes from Latin and means “equal night.” It’s the day the Sun shines almost equally on both the Northern and Southern Hemispheres. This happens when the center of the Sun crosses the Earth’s equator in the sky.
Even though it’s called “equal night,” daylight still lasts a little longer. That’s because we don’t see the Sun as just a point—we see its whole disc. We count sunrise as when any part of the Sun appears, and sunset as when the last bit disappears. This adds a few extra minutes of light to our day.
Why the Sky Looks Different
During the equinox, the Sun begins to move lower in the sky each day. This creates longer shadows and a softer, golden light. The Earth’s atmosphere also bends sunlight. This bending, called refraction, makes the Sun look a little higher in the sky than it actually is. Because of this, we see the Sun even when it’s still just below the horizon.
This extra angle adds even more daylight. The closer you are to the North or South Pole, the more minutes you gain. This effect also helps decide when we see the Harvest Moon, which is the full Moon closest to the equinox.
Different Seasons Around the World
In the Northern Hemisphere, the September equinox marks the start of fall. But in the Southern Hemisphere, it signals the beginning of spring. While we pull out sweaters, they’re getting ready for warmer weather and blooming flowers.
Take time to step outside on September 22. Whether you’re watching the sunset, walking through fallen leaves, or looking up at the stars, the autumn equinox is a reminder that nature moves in balance—even if only for a moment.
