You’re probably already thinking about it. That first morning where the air doesn’t feel like a warm wet blanket and you can actually wear a hoodie without sweating through your shirt in ten minutes. We all want to know when fall starts 2025, but the answer depends entirely on who you ask—a meteorologist, an astronomer, or your local barista who just put pumpkin spice back on the menu.
Honestly, it’s a bit of a mess.
If you go by the astronomical calendar, which is what most people mean when they look at a wall calendar, autumn officially arrives on Monday, September 22, 2025. Specifically, the autumnal equinox hits at 6:19 PM EDT. That is the exact moment the sun crosses the celestial equator, heading south. Day and night are basically equal in length, though not perfectly. It’s a cosmic balancing act.
But here’s the thing.
✨ Don't miss: The Truth About Black Button Down Shirts for Women and Why Your Closet Is Missing One
If you talk to a weather person, they’ll tell you fall actually starts on September 1. They don't care about the tilt of the Earth or the position of the sun. They care about clean data. By grouping September, October, and November together, they get a consistent three-month block to track climate trends. It’s practical. It’s less "celestial magic" and more "Excel spreadsheet."
The Science of the September 22 Equinox
So, what actually happens at 6:19 PM on that Monday?
The Earth doesn't just suddenly tilt. It’s always tilted at about 23.5 degrees. But as we orbit the sun, there are two points in the year where the tilt is neither away from nor toward the sun. That’s the equinox. The word comes from the Latin aequus (equal) and nox (night).
For those of us in the Northern Hemisphere, it’s the transition into shorter days. In the Southern Hemisphere? They’re actually heading into spring. It’s a reminder that our seasonal "start dates" are entirely a matter of perspective.
There’s also a weird phenomenon called atmospheric refraction. Even though the sun technically sets at a specific time, the Earth’s atmosphere bends the light, making it look like the sun is still above the horizon for a few minutes after it’s actually gone. This means that on the day when fall starts 2025, you’ll actually have a few more minutes of daylight than darkness. The true "equal day and night" (the equilux) usually happens a few days after the equinox.
Why the Date Changes Every Single Year
You might remember fall starting on September 21 or September 23 in previous years. It isn't a glitch in the matrix.
The Earth takes about 365.24 days to orbit the sun. Our calendar only has 365 days. That extra quarter of a day adds up, which is why we have leap years every four years to "reset" the clock. This slight drift causes the timing of the equinox to shift by about six hours every year. In 2025, we land on the 22nd.
In some years, the equinox can even fall on September 24, though that hasn't happened since 1931 and won't happen again until 2303. Usually, it's a toss-up between the 22nd and the 23rd.
Meteorological vs. Astronomical: The Great Debate
Meteorologists are the "early birds" of the season. For them, summer is June, July, and August. Period.
Why? Because it’s easier to compare 2025 to 1985 if the months are identical. If you use the astronomical dates, the "start" of fall moves around, making it a nightmare to calculate average monthly temperatures. If you’re a gardener or someone who watches the local news for frost warnings, you probably lean toward the meteorological definition. It aligns better with when the leaves actually start turning and the "feel" of the air changes.
When Do the Leaves Actually Change in 2025?
Knowing when fall starts 2025 on paper is one thing. Knowing when the mountains turn orange is another.
The "peak" foliage season is dictated by two main factors: photoperiod (the length of daylight) and temperature. While the daylight hours are fixed by the calendar, the temperature is the wild card.
- The Drought Factor: If we have a very dry summer in 2025, the leaves might turn early but look "crispy" or brown rather than vibrant.
- The Temperature Factor: We need those crisp, cool nights (above freezing but below 45°F) to trigger the breakdown of chlorophyll and reveal the hidden yellows and oranges.
- The Sugar Factor: Bright, sunny days in September help produce the anthocyanins that give us those deep reds and purples.
According to long-range projections from the Old Farmer’s Almanac and NOAA’s Climate Prediction Center, parts of the Northeast and Upper Midwest typically see peak colors between early and mid-October. If 2025 follows the recent trend of "delayed autumns" due to warming nighttime temperatures, we might see the best colors pushed back into late October for many regions.
Cultural Weirdness and the "Vibe" Shift
For a huge chunk of the population, fall starts when the NFL kicks off or when the local Starbucks starts smelling like a spice rack.
✨ Don't miss: Finding the Perfect Picture of Orange Tree: What Most Photographers Get Wrong
Labor Day is often the "soft launch" of autumn. In 2025, Labor Day is September 1. It’s the unofficial end of summer, the day the pools close, and the day people start buying oversized sweaters even if it’s still 85 degrees outside.
Then you have the Harvest Moon. In 2025, the Harvest Moon—which is the full moon closest to the autumnal equinox—falls on October 6. This is a bit later than usual. Historically, the Harvest Moon was vital because it provided extra light for farmers to work late into the evening, bringing in the crops before the first frost.
Preparing for the 2025 Season
Don't just wait for the calendar to flip. If you want to actually enjoy the transition, you have to be proactive.
Weather patterns are getting weirder. We see "False Springs" and "Second Summers" more often now. It’s entirely possible that on September 22, 2025, you’ll be sitting in 90-degree heat.
- Check your HVAC now. Don't wait until the first 40-degree night in October to find out your furnace is making a clicking sound.
- Plant your bulbs. If you want tulips and daffodils in 2026, they need to go in the ground once the soil temperature drops below 60 degrees—usually a few weeks after the equinox.
- Watch the sunset. Between September 1 and September 22, the sun will set about 2-3 minutes earlier every single day. You can literally feel the season slipping away if you pay attention to the shadows on your floor.
Autumn is a short-lived bridge between the intensity of summer and the hibernation of winter. Whether you mark it by the sun’s position on September 22 or the first time you see your breath in the morning air, it's a reminder to slow down.
Next Steps for Fall 2025 Prep:
- Audit your gear: Pull out your cold-weather coats and boots by mid-September to check for moths or salt damage from last year.
- Track the foliage: Bookmark the Smoky Mountains Foliage Prediction Map which usually updates its interactive tool in late August to show exactly when your zip code will peak.
- Adjust your lighting: As the "Great Dimming" begins, consider swapping out a few lightbulbs for warmer tones to offset the loss of natural blue light in the afternoons.