Tornado Alley
Although the official boundaries of Tornado Alley are not clearly defined, its core extends from northern Texas, Oklahoma, Kansas, Nebraska, into South Dakota. States such as Missouri, Iowa, Minnesota, Wisconsin, Illinois, Indiana, and western Ohio are sometimes included in Tornado Alley. Some research suggests that tornadoes are becoming more frequent in the northern parts of Tornado Alley where it reaches the Canadian prairies.
Tornado Alley
Over the years, the location(s) of Tornado Alley have not been clearly defined. No definition of tornado alley has ever been officially designated by the National Weather Service (NWS). Thus, differences in location are the result of the different criteria used.