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.

Fall weather is soon going to be hitting the Northeast and just in time as the official start to fall — the autumnal equinox — is about to arrive. The fall — or autumnal — equinox can land on Sept. 22 or 23 depending on the year This year,

The official start to the fall season, the autumnal equinox, occurs on Sunday, Sept. 22. What exactly happens during the equinox? Here’s a breakdown: According to NOAA, an equinox occurs when the Earth’s axis is tilted neither away nor toward the sun.