The phenomenon is not exclusive to North America, though it goes by different names around the world. In the United Kingdom, a similar late-season warm spell is often called an Old Wives' Summer or St. Luke’s Little Summer. In Germany and much of Central Europe, it is known as Altweibersommer. In South America, particularly in Brazil and Argentina, a similar warm break in the autumn is called Veranico de Santa Rosa.
The term Indian summer most commonly refers to a period of unseasonably warm, dry, and hazy weather that occurs in late autumn, typically after the first frost has hit. Beyond the weather, "Indian Summer" is also the title of several popular creative works, including a critically acclaimed PBS television series and a nostalgic 1990s film. Wikipedia +4 Weather Phenomenon Meteorologically, an Indian summer is characterized by calm winds, hazy skies, and clear, chilly nights. Britannica +1 Timing: It usually occurs in October or November in the Northern Hemisphere. Criteria: According to the Old Farmer’s Almanac , it must follow a cold spell or frost and include a high-pressure system that keeps the air stable and hazy. Origin: The term likely originated in New England, possibly referring to the time when Native Americans gathered winter stores or because the hazy conditions resembled smoke from prairie fires. Britannica +3 TV Review: Indian Summers (PBS/Channel 4) This period drama is set in 1932 Simla, the summer capital of British India, against the backdrop of the declining British Empire. NPR +1 14 sites TV Review: 'Indian Summers' - Variety Sep 24, 2015 — whats an indian summer