While Indian Summer is not the formal name of any time of year, it is a commonly used expression that describes the sunny, warm days of fall after the color of the leaves start to change and after a frost, but before any snowfall has occurred. As the Farmers' Almanac describes, Indian summer” is a phrase most North Americans use to describe an unseasonably warm and sunny patch of weather during autumn. Also, because the transition period of warm weather to cool weather progresses from the north to the south, Indian Summers may occur numerous times during the year, if in different parts of the country.