what months are fall
n. 1  1. The season of the year between summer and winter, during which the weather becomes cooler and many plants become dormant, extending in the Northern Hemisphere from the autumnal equinox to the winter solstice and popularly considered to include the months of September, October, and November; fall.
Meteorologists (and most of the temperate countries in the southern hemisphere) use a definition based on months, with autumn being September, October and November in the northern hemisphere, and March, April and May in the southern hemisphere.