In the midwest a warm spell following the first major frost in October is called "Indian Summer." It was made popular by John McCutcheon's famous 1907 depiction called "Injun Summer" and published in the Chicago Tribune for many years from 1912 to 2002.

http://www.tkinter.smig.net/Chicago/InjunSummer/index.htm

Chief Black Hawk is overlooking the Rock River and his Indian spirits (trees in full color) in Lowden State Park.