- Indian summerThis term is more than 200 years old and probably originates from a time when native people in North America relied on these warm days to harvest their crops. Today, Indian summer refers to the sunny, dry and unusually warm days which occur in the autumn and are usually preceded by a snowfall, hard frost or spell of cool, windy and stormy weather. During an Indian summer, the winds are either light or calm and the air is often hazy blue or smoky. - Date modified: