Fall began on Wednesday with the rising of a full moon. The Harvest Moon, so-called because of the extra light it gave farmers to work later for bringing in their crops, rose on the autumnal equinox, a rare cosmic event which hasn't happened for almost 20 years. It won't happen again until 2029.
According to the National Aeronautics and Space Administration (NASA), the action began at sunset on Sept 22, the last day of the northern summer: "As the sun sinks in the west, bringing the season to a close, the full Harvest Moon will rise in the east, heralding the start of fall. The two sources of light will mix together to create a kind of 360-degree, summer-autumn twilight glow that is only seen on rare occasions."