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
Another third of Canadian tornadoes strike Southern Ontario, especially in the region halfway between the Great Lakes from Lake St. Clair to Ottawa. This happens because tornadoes in this region are triggered or augmented by lake breeze fronts from Lake Huron, Lake Erie, Lake Ontario, and Georgian Bay. Tornadoes do not often hit lake shadow regions, although they are not unknown, and some, such as the 2011 Goderich, Ontario tornado, have been violent. However, most Ontario tornadoes are concentrated in a narrow corridor from Windsor and Sarnia through London, and then northeast to Barrie and Ottawa. Tornadoes up to EF4 in strength have been documented in this region.