Indian Summer
Indian Summer, a period of summerlike weather that occurs between the first frost of autumn and the onset of winter, notably in the central and Atlantic coast states and in Canada. It may last from one or two days to a week or two. Indian summer is caused by a gigantic mass of warm air which, carried north from the tropics, forms into layers that lie stagnant over eastern North America. The motionless atmosphere cannot carry away smoke and dust from the land's surface, creating a characteristic haze, which is particularly noticeable at the horizon.
There are many stories attempting to explain the origin of the term Indian summer but none is known to be authentic.
A similar period of warm, hazy weather in Europe is called second summer in some countries. In Germany it is called old women's, or old wives', summer; in Poland, God's gift to Poland; and in England, St. Martin's summer, or all-hallow summer.