The Northern Hemisphere marks the autumnal equinox on Friday, September 22, 2017, at exactly 4:02 P.M. EDT. The Autumnal equinox—also called the September equinox—is the astronomical start of fall in the Northern Hemisphere and spring in the Southern Hemisphere. The word equinox means “equal night”; night and day are about the same length of time. During the equinox, the Sun crosses what we call the “celestial equator” (just imagine the line that marks the equator on Earth extending up into the sky) from north to south. At this point, the amount of nighttime and daytime are roughly equal to each other. From here on out, the temperatures begin to drop and the days start to get shorter than the nights. The Old Farmer’s Almanac is a great reference for all things weather, astronomy, moon phases, gardening, food and just about everything! Check it out.