Tornado Alley
States such as Missouri, Iowa, Minnesota, Wisconsin, Illinois, Indiana, and western Ohio are sometimes included in Tornado Alley. Research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies.
Tornado outbreak
The tornadoes usually occur within the same day, or continue into the early morning hours of the succeeding day, and within the same region. Most definitions allow for a break in tornado activity (time elapsed from the end of last tornado to the beginning of next tornado) of six hours. If tornado activity indeed resumes after such a lull, many definitions consider the event to be a new outbreak. A series of continuous or nearly continuous tornado outbreak days is a tornado outbreak sequence. Tornado outbreaks usually occur from March through June in the Great Plains of the United States and Canada, the Midwestern United States, and the Southeastern United States in an area colloquially referred to as Tornado Alley. Tornado outbreaks do occur during other times of the year and in other parts of the world, however. A secondary less active and annually inconsistent tornado "season" in the U.S. occurs in late autumn.