You’re probably already seeing the pumpkin spice takeover at the local coffee shop, but let's be real—the weather usually hasn't gotten the memo yet. If you're looking for the exact moment you can officially swap your sandals for boots, the timing is actually quite precise.
The Exact Moment Fall Starts 2025
In the Northern Hemisphere, astronomical fall officially begins on Monday, September 22, 2025, at 2:19 p.m. EDT. For those of you on the West Coast, that’s 11:19 a.m. PDT. This isn't just a date someone picked out of a hat; it's a specific cosmic event called the autumnal equinox. At that exact second, the sun crosses the celestial equator, heading south. Basically, the Earth’s axis isn't tilting toward or away from the sun. It’s sitting perfectly upright for a fleeting moment.
Honestly, it's kinda wild how precise the universe is. While we’re stuck in traffic or deciding what to have for lunch, the planet is hitting a literal tipping point in its orbit.
Why "Equinox" is Sorta a Lie
Most people will tell you that the equinox means "equal day and night." The word even comes from the Latin aequus (equal) and nox (night). It sounds great on paper, but if you look at your weather app on September 22, you’ll notice something annoying.
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The day is actually longer than the night.
Why? Atmospheric refraction. The Earth’s atmosphere acts like a lens and bends the sun’s light. This makes the sun appear above the horizon even when it’s technically below it. You get a few extra minutes of light in the morning and evening that shouldn't be there. If you want a day where the sun is actually up for exactly 12 hours, you’ll have to wait for the equilux, which usually happens a few days after the equinox.
Meteorological vs. Astronomical Fall
There is a massive debate—well, maybe just a friendly disagreement—between astronomers and meteorologists about when fall actually starts.
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Meteorologists are all about simplicity. They don't want to deal with a start date that jumps around between the 21st and 24th of September because of leap years and orbital wobbles. For them, meteorological fall started on September 1, 2025. They group the seasons into clean, three-month blocks:
- September, October, and November are Fall.
- December, January, and February are Winter.
It makes tracking climate data and temperature averages way easier. If you’re a "September 1st is the start of fall" person, you’re technically following the meteorological calendar. If you wait for the equinox, you’re an astronomy purist. Both are right, but your local weather forecaster is likely looking at the September 1st date to tell you if this year is "warmer than average."
What to Expect This Year
Since the fall start 2025 falls on a Monday, it’s a bit of a mid-day transition. While the calendar says autumn, the atmosphere often lags behind. This is called seasonal lag. The oceans and land take a while to cool down after a long summer, which is why we often get those "Indian Summer" heatwaves late in the month.
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However, once we pass that September 22nd marker, the Northern Hemisphere starts losing daylight at its fastest rate of the year. We’re talking about losing roughly one to three minutes of light every single day depending on how far north you live.
Strange Equinox Facts
- The Aurora Spike: NASA has noted that geomagnetic storms—those things that cause the Northern Lights—are twice as likely to happen during the weeks around the equinox compared to summer or winter.
- Due East and West: This is the only time of year (along with the spring equinox) when the sun rises exactly due east and sets exactly due west. It’s a great day to recalibrate your sense of direction.
- The Harvest Moon: In 2025, the Harvest Moon—the full moon closest to the equinox—actually arrives a bit late, on October 7. Traditionally, this extra moonlight helped farmers work late into the night to bring in crops.
Your Autumn Checklist
Don't let the season sneak up on you. Since the official start is September 22, use the weeks leading up to it to prep.
- Check your furnace filters now. You don't want to find out they're clogged on the first 40-degree night.
- Clean the gutters. Once the leaves start dropping in late September, you’ll want a clear path for the October rain.
- Switch your skincare. The air gets significantly drier after the equinox. Swapping a light lotion for a heavier cream can save your skin before the winter cracks start.
- Update your emergency car kit. Add a blanket and a flashlight. The sun will be setting much earlier before you know it.
The transition into fall is more than just a date on a calendar; it's a massive shift in how the planet interacts with the sun. Whether you celebrate the meteorological start on the 1st or wait for the astronomical equinox on the 22nd, the change is inevitable. Watch the shadows get longer and the light get "gold" around 4:00 p.m.—that's the real signal that the season has shifted.