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When is fall 2023? Autumn equinox explained

What is fall equinox: EXPLAINED
What is fall equinox: EXPLAINED 00:23

PHILADELPHIA (CBS) -- You can already start to feel it in the air. Cool, crisp weather is a signature of the fall season, but fall doesn't actually begin until the autumn equinox.

When is the fall equinox 2023?

This year, the autumn equinox will begin on Saturday, September 23, at 2:50 a.m. and will last until the winter solstice on Thursday, December 21, at 10:27 a.m. 


While the September equinox usually occurs on September 22 or 23, it can very rarely fall on September 21 or September 24. A September 21 equinox has not happened for several millennia. In the 21st century, it will happen twice—in 2092 and 2096. The last September 24 equinox occurred in 1931, the next one will take place in 2303, according to CBS News Philadelphia Meteorologist Andrew Kozak.  

The equinox dates vary because of the difference between how the Gregorian calendar defines a year (365 days) and the time it actually takes for Earth to complete its orbit around the sun (about 365 and 1/4 days).  

What is a solar equinox?

The equinox happens twice a year (spring and fall) when the Earth's axis is titled neither toward nor away from the sun, meaning that the equinoxes are the only time when both the Northern and Southern Hemispheres experience "nearly" equal amounts of daylight and darkness at all latitudes, according to the National Weather Service. The sun will be directly overhead at noon during the equinox. 

This event is different than the summer and winter solstices, when the Earth's tilt is its furthest either toward or away from the sun.  

After the autumn equinox, there will be earlier sunsets and later sunrises in the Northern Hemisphere, meaning the days will get shorter and shorter as we head toward the winter solstice. 

The equinox will also actually help change the colors of the leaves and summon them to fall. Chemicals -- such as flavonoids, carotenoids and anthocyanins -- become more prominent in leaves after the autumn equinox while Chlorophyll decreases, resulting in the vibrant ambers, reds and yellows of autumn, Kozak said. 

What does "equinox" mean?

The word equinox is derived from the two Latin words aquus (equal) and nox (night). The fall equinox also begins the Libra season, or sun sign, which is often known to represent balance, equanimity and harmony.

Equinoctial disruptions and sun outages

"Sun outages" can occur around the equinoxes. They typically occur in the days after the September equinox, according to National Geographic. Solar radiation can interfere with and even stop satellites transmitting signals during these events, as many satellites orbit around the equator and can become "flooded with direct solar radiation." Consumer could experience slow itnernet connections, radio static or even frozen television screens. 

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