Autumn (known as fall in North American English) is one of the four temperate seasons. Autumn marks the transition from summer into winter, usually in March (southern hemisphere) or September (northern hemisphere) when the arrival of night becomes noticeably earlier. Meteorological Offset Astronomical Northern hemisphere 1 September – 30 November Autumnal equinox (22-23 September) – Winter solstice (21–22 December) http://www.usno.navy.mil/USNO/astronomical-applicati… (More on Autumn)