Fall Begins: Autumn Equinox was at 7:49 a.m. PST Saturday

Summer officially ended at 7:49 a.m. Pacific Standard Time Saturday. That's the moment when the Autumnal Equinox occured in the Western United States, according to the Old Farmer's Almanac.

The Alamanac explains what's happening.

On the first day of fall—the autumnal equinox—day and night are each about 12 hours long (with the actual time of equal day and night, in the Northern Hemisphere, occurring a few days after the autumnal equinox). The Sun crosses the celestial equator going southward; it rises exactly due east and sets exactly due west.

Days and nights also have equal length in the spring equinox, too. On Saturday, sunrise occured at 6:38 a.m. in western Riverside County, with sunset expected at 6:45 p.m.

Throughout history, groups have celebrated the autumn equinox, partly because it represents harvest time.

And don't worry, there is still time before the clocks "fall back" to mark the end of Daylight Saving Time at 2 a.m. Sunday, Nov. 4.