Fall foliage at sunrise on the Blue Ridge Parkway near Asheville, North Carolina. The September Equinox 2025 arrives Sept. 22 at 2:19 p.m. EDT, marking autumn in the north and spring in the south.
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When is the equinox? Astronomical autumn begins this year on Monday, Sept. 22, 2025, with 2:19 p.m. EDT the precise moment of the September equinox. At that instant, Earth’s tilted axis will be side-on to the sun, producing almost equal amounts of daylight and darkness across the globe.
Here’s everything you need to know about the September 2025 equinox.
Equinox 2025: When Does Fall Begin?
The equinox marks the beginning of astronomical fall in the Northern Hemisphere and astronomical spring in the Southern Hemisphere. Astronomers rely on equinoxes and solstices, the four turning points of Earth’s annual journey around the sun, to determine the seasons. However, meteorologists mark seasons by calendar months, so by now you’ll have heard weather forecasters talking for weeks about the beginning of fall.
Equinox 2025: Why The Equinox Happens
It’s all a story about Earth’s axis, which is tilted 23.4 degrees relative to its orbit around the sun. That tilt causes the sun to appear to migrate north and south of the equator during the year. For example, the Northern Hemisphere is tipped toward the sun at the June solstice and tipped away from it on the December solstice. It means long days in June and short days in December. In the Southern Hemisphere, the opposite is the case. The equinoxes in March and September are the transition points, when neither hemisphere leans toward the sun. The word “equinox” comes from Latin for “equal night.”
The illumination of Earth as it orbits the sun.
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Equinox 2025: Why Day and Night Aren’t Exactly Equal
The length of day and night on the equinoxes isn’t actually equal across the globe. The culprit here is Earth’s atmosphere, which bends sunlight, making the sun appear to be above the horizon a few minutes before it actually rises, and remain in the sky a little beyond its actual setting. The effect varies by latitude, with slightly longer days the farther you travel from the equator. However, across the globe, the day is still slightly longer than the night, according to Timeanddate.com.
Nor is the timing of the equinox fixed. Earth’s slightly irregular orbit of 365.25 days means the equinox can fall anywhere between Sept. 21 and 24, depending on the year.
Equinox 2025: Observing Tips
The best way to experience the equinox isn’t to wait until noon and see where the sun is, but to watch a sunrise and/or sunset. Throughout the year, the sunrise and sunset point migrate either side of due east and due west, respectively. Only on the equinoxes in March and September does the sun rise due east and set due west.
Wishing you clear skies and wide eyes.