Illinois Weather Trivia for October 20th
- Indian Summer is defined as a mid to late autumn period of abnormally warm weather. For a late-season warm spell to really be considered "Indian Summer", it should follow at least one killing frost, and preferably a substantial period of chilly weather. Traditional Indian Summer weather is characterized by sunny, calm, mild days and clear, cool nights, with haze or smoke in the air.
Select Other Dates for Illinois Weather Trivia