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When does fall start? A look at the autumn equinox

Plus, how meteorologists get "early access" to fall.

Fall is just around the corner! The autumn equinox will mark the change of seasons on Thursday, Sept. 22. 

Seasons — and the way we mark them — come from the Earth's tilt as it orbits the sun. The spring and autumn equinoxes are the only times of the year when the Earth's axis is tilted neither toward or away from the sun. 

During the equinox, the sun will shine directly on the equator and bring nearly equal amounts of day and night. It's even in the name — "equinox" comes from the words for "equal" and "night" in Latin.

That doesn't mean we're actually getting equal day and night, though. The Earth's atmosphere refracts light and causes us to see daylight before the sun is actually above the horizon. 

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"What's interesting is because of the way our time zones are set up, and the way we measure sunrise and sunset, in each location, it may not be equal day and equal night on the equinox," TEGNA meteorologist Brad Panovich said. "Sometimes it falls a couple of days before or a couple of days after."

Looking to add to your astronomical vocabulary? The time when day and night are actually equal is known as the "equilux."

For most of the U.S., it certainly doesn't feel like fall just yet. But it might soon be time to get your sweaters out of storage. 

"Typically, there's a magic time right around mid-September, where we start to see cold fronts moving into the lower 48 (states)," Panovich said. "So once you start to see cold fronts, you tend to see at least drier air and eventually cooler air."

Early access?

For some people, it's been autumn for weeks. Not pumpkin spice enthusiasts — meteorologists! Meteorological seasons help experts keep track of what's happening on Earth, like temperature changes and weather patterns. They always start on the first of a month. For fall, that's Sept. 1. 

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Astronomical seasons, which most people follow, vary year-to-year. The uniformity of meteorological seasons helps scientists compare data over long periods of time.

When does winter start in 2022? 

Winter starts in the Northern Hemisphere with the winter solstice on Dec. 21. The summer solstice is the longest day of the year, while the winter solstice is the shortest. 

Want to cast your shortest shadow? 

It may be too early for a lot of traditional fall activities, but there's one science-y trick you can show your kids. 

"So if you go outside at solar noon, on the equinox, you actually will have the smallest shadow that you could cast year round," Panovich said. "So you've got to have sunny skies, obviously. But it's a cool thing to do with the kids." 

Solar noon is different from standard noon -- it's when the sun is at its highest point in the sky from your location. The National Oceanic and Atmospheric Administration has an online calculator where you can find solar noon at your desired location. 

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