Autumn is generally defined in the Northern Hemisphere as the period between the autumnal equinox (day and night of equal length), September 22 or 23, and the winter solstice (the shortest day of the year), the 21st. December 22th; and in the southern hemisphere as the period between March 20 or 21 and June 21 or 22. The autumn temperature transition between the heat of summer and the cold of winter occurs only at mid and high latitudes; in equatorial regions, temperatures generally vary little throughout the year. In the polar regions, on the other hand, autumn is very short.
The equinox occurs at two times of the year when the Sun is perpendicular to the equator, and the day and night have the same duration. That is why we call it ‘equinox’, which comes from the Latin: ‘æquus’ (equal) and ‘nox’ (night).
According to the astronomical definition of the seasons, the autumnal equinox also marks the beginning of autumn for the northern hemisphere, while, in the southern hemisphere, the first day of spring. The Earth’s axis is tilted at an angle of 23.4º , which implies that one hemisphere will always be more inclined than another towards the Sun. During that period of time and until the next equinox, that hemisphere receives more Sun than the other. .
The concept of autumn in European languages is related to the harvesting of crops ; In many cultures, autumn, like the other seasons, has been marked by rituals and festivals that revolve around the importance of the season in food production. Animals gather food in the fall to prepare for the upcoming winter, and those with fur often develop thicker coats. Many birds migrate to the equator to escape the low temperatures.
A common fall phenomenon in the central and eastern United States and in Europe is the Indian summer, a period of unusually warm weather that sometimes occurs in late October or November.
