Autumn Landscape. Autumn, also known as fall in North American English, is one of the four temperate seasons. Autumn marks the transition from summer to winter, in September or March, when the duration of daylight becomes noticeably shorter and the temperature cools considerably. One of its main features in temperate climates is the shedding of leaves from deciduous trees. Some cultures regard the autumnal equinox as mid-autumn, while others with a longer temperature lag treat it as the start of autumn. Meteorologists use a definition based on Gregorian calendar months, with autumn being September, October, and November in the northern hemisphere, and March, April, and May in the southern hemisphere. Persians celebrate the beginning of the autumn as Mehregan to honor Mithra. In North America, autumn traditionally starts with the September equinox and ends with the winter solstice. Popular culture in the United States associates Labor Day, the first Monday in September, as the end of summer and the start of autumn; certain summer traditions, such as wearing white, are discouraged after that date. As daytime and nighttime temperatures decrease, trees change color and then shed their leaves. In traditional East Asian solar term, autumn starts on or around 8 August and ends on or about 7 November. In Ireland, the autumn months according to the national meteorological service, are September, October and November. However, according to the Irish Calendar, which is based on ancient Gaelic traditions, autumn lasts throughout the months of August, September and October, or possibly a few days later, depending on tradition. The names of the months in Manx Gaelic are similarly based on autumn covering August, September and October. In Argentina, Australia and New Zealand, autumn officially begins on 1 March and ends on 31 May. The word autumn comes from the ancient Etruscan root autu-and has within it connotations of the passing of the year. It was borrowed by the neighbouring Romans, and became the Latin word autumnus. After the Roman era, the word continued to be used as the Old French word autompne or autumpne in Middle English, and was later normalised to the original Latin. In the Medieval period, there are rare examples of its use as early as the 12th century, but by the 16th century, it was in common use. Before the 16th century, harvest was the term usually used to refer to the season, as it is common in other West Germanic languages to this day. However, as more people gradually moved from working the land to living in towns, the word harvest lost its reference to the time of year and came to refer only to the actual activity of reaping, and autumn, as well as fall, began to replace it as a reference to the season. However, these words all have the meaning to fall from a height and are clearly derived either from a common root or from each other. The term came to denote the season in 16th-century England, a contraction of Middle English expressions like fall of the leaf and fall of the year. Compare the origin of spring from spring of the leaf and spring of the year. During the 17th century, English emigration to the British colonies in North America was at its peak, and the new settlers took the English language with them. While the term fall gradually became nearly obsolete in Britain, it became the more common term in North America. The name backend, a once common name for the season in Northern England, has today been largely replaced by the name autumn. Association with the transition from warm to cold weather, and its related status as the season of the primary harvest, has dominated its themes and popular images. In Western cultures, personifications of autumn are usually pretty, well-fed females adorned with fruits, vegetables and grains that ripen at this time. Many cultures feature autumnal harvest festivals, often the most important on their calendars. Still extant echoes of these celebrations are found in the autumn Thanksgiving holiday of the United States and Canada, and the Jewish Sukkot holiday with its roots as a full-moon harvest festival of tabernacles. There are also the many North American Indian festivals tied to harvest of ripe foods gathered in the wild, the Chinese Mid-Autumn or Moon festival, and many others. The predominant mood of these autumnal celebrations is a gladness for the fruits of the earth mixed with a certain melancholy linked to the imminent arrival of harsh weather.