Autumn, also known as fall in American and Canadian English, is one of the four temperate seasons. Autumn marks the transition from summer to winter, in September (Northern Hemisphere) or March (Southern Hemisphere), when the duration of daylight becomes noticeably shorter and the temperature cools down considerably. One of its main features is the shedding of leaves from deciduous trees.
In North America, autumn is usually considered to start with the September equinox (21 to 24 September) and end with the winter solstice (21 or 22 December). Popular culture in North America associates Labor Day, the first Monday in September, as the end of summer and the start of autumn.