What is a period of unseasonably warm, dry weather that sometimes occurs in autumn called?

An Indian summer is a period of unseasonably warm, dry weather that sometimes occurs in autumn in Northern America and other temperate regions of the world during September to November. In an article on the US National Weather Service's web site, weather historian William R. Deedler writes that Indian Summer can be defined as "any spell of warm, quiet, hazy weather that may occur in October or November." It is usually described as occurring after a killing frost.

Although the exact origins of the term are uncertain, it was perhaps so-called because it was first noted in regions inhabited by American Indians, or because the Indians first described it to Europeans, or it had been based on the warm and hazy conditions in autumn when American Indians hunted. In addition to such conjectures, a great depth of Native American folklore is attributed to describing this phenomenon.