The 2026 autumn equinox marks the astronomical start of autumn in the Northern Hemisphere on September 22 or 23ScienceSep 21 at 11:12 AM – Sep 22 at 4:44 AM3 outletsBBC NewsAutumn equinox 2026: When is it and what happens? Sep 21 at 8:05 PMEvening StandardThe best ways to celebrate the Autumn Equinox in London seen Sep 22 at 4:44 AMThe OregonianFall officially arrives this week — here's exactly when the season begins in Oregon Sep 21 at 2:34 PMAutumn officially starts with the fall equinox on Sept. 22, 2026 Sep 21 at 11:12 AM