It's almost time to fall into fall, though in many parts of the country, it feels like we're already there. There are specific times when the astronomical seasons officially turn over -- for fall, it's the autumnal equinox.

The official first day of fall, otherwise known as the autumnal equinox, is this weekend in the Northern Hemisphere. According to Encyclopedia Britannica, it is one of only two days, the other being the vernal equinox, when the sun is directly above the Equator, essentially dividing night and day into equal portions.

During an equinox, places around the globe experience nearly equal amounts of daytime and nighttime. The second occurrence this year happens on Sunday.

The autumnal equinox on Sept. 22 marks the start of fall, bringing equal day and night in the Northern Hemisphere.

The autumnal equinox is considered the first day of fall, but it’s so much more than that. The word equinox comes from two Latin words: “aequus,” meaning equal, and “nox,” meaning night, the National Weather Service explains on its website.