Springfield, IL – The official start of fall is just days away. The autumnal equinox arrives Monday, Sept. 22, at 11:19 a.m. PT, marking the moment when day and night are nearly equal across the globe.
According to the National Weather Service, the equinox occurs when Earth’s axis is tilted neither toward nor away from the sun, creating a balance of daylight and darkness at almost all latitudes. This balance happens only twice a year: in September and in March.
During Monday’s equinox, the sun will rise almost exactly in the east and set almost exactly in the west, making it the best natural compass of the year. It’s also when sunrises and sunsets appear and disappear the fastest, as the sun crosses the horizon at its steepest angle.
From space, the change is striking. NASA’s Earth Observatory shows a distinct line—called the “terminator”—splitting daylight and darkness evenly down the middle of the planet. This visual highlights how sunlight shifts as Earth orbits the sun.
While the event looks like an ordinary day on the ground, the equinox is celebrated as the official start of autumn in the Northern Hemisphere. Many mark it with seasonal traditions—like fall hikes, sweater weather, or pumpkin spice lattes—as leaves begin to change in the coming weeks.
The next major astronomical milestone will be the winter solstice on Dec. 21, when the Northern Hemisphere experiences its shortest day and longest night of the year.
