Harvest Moon with Century Saguaro (over 100 years old) against the Santa Catalina Mountains of southern Arizona, via Randall Kayfes.
The moon turns precisely full on September 6 at 3:03 a.m. EDT, 2:03 a.m. CDT, 1:03 a.m. MDT and 12:03 PDT. That’s why we say the full moon falls on the night of September 5, for the Americas.
Is this September full moon the Harvest Moon? Not precisely, but it’ll act like one.
More often than not, the September full moon is the Northern Hemisphere’s Harvest Moon. The Harvest Moon is usually defined as the full moon closest to the autumn equinox, which – in the Northern Hemisphere – comes on or near September 22 each year.
Last year’s Harvest Moon fell in September. Next year’s Harvest Moon will, too.
But, in 2017, the September 6 full moon comes too early to be the Northern Hemisphere’s official Harvest Moon, according to the most widely accepted definition of the term. That’s because the full moon of October 5, 2017, will fall closer to this year’s September 22 equinox. The October 2017 full moon will be this year’s Harvest Moon, while the September 5-6 full moon will carry its ordinary monthly full moon name of Fruit Moon in the Northern Hemisphere (and Worm Moon, Lenten Moon, Crow Moon, Sugar Moon, Chaste Moon or Sap Moon in the Southern Hemisphere). Read more about full moon names.
However, in most respects, the September 2017 and October 2017 full moons can be regarded as Harvest Moon co-stars. By that we mean that both have the characteristics of a Harvest Moon. The primary Harvest Moon characteristic has to do with the moonrise. On the average, the moon rises some 50 minutes later with each passing day. Around the time of the full Harvest Moon, the lag time between successive moonrises is reduced to a yearly low.
In 2017, there’s no appreciable difference between the lag in moonrise times associated with September and October full moons. In both of these months, the moon rises a shorter-than-usual time after sunset for several evenings in a row, following the date of full moon.