The Northern Hemisphere, the northern half of the earth, has autumn weather during late September, October, and November. Autumn weather does not last so long in the polar region, where extremely cold winter weather begins earlier. In tropical regions, seasonal changes are not great. The Southern Hemisphere has autumn from March until early June. Many people call this season fall because it is the period of falling leaves.
Autumn is also harvest time for many crops.
In North America, early autumn days are generally warm and nights are cool. As winter approaches, the air becomes chillier and frost often occurs at night. In much of North America, the end of autumn is marked by the freezing of lakes and streams, southern migration of birds, and prewinter snowstorms. Hurricanes cause great damage along the coasts of the Gulf of Mexico and the western North Atlantic Ocean. Collecting and identifying leaves that have fallen from trees is a favorite autumn activity.