Tornado Alley
It has also been asserted that there are numerous Tornado Alleys. In addition to the Texas/Oklahoma/Kansas core, such areas include the Upper Midwest, the lower Ohio Valley, the Tennessee Valley and the lower Mississippi valley. Some studies suggest that there are also smaller tornado alleys located across the United States.
Michigan
The state averages 30 days of thunderstorm activity per year. These can be severe, especially in the southern part of the state. The state averages 17 tornadoes per year, which are more common in the state's extreme southern section. Portions of the southern border have been almost as vulnerable historically as states further west and in Tornado Alley. For this reason, many communities in the very southern portions of the state have tornado sirens to warn residents of approaching tornadoes. Farther north, in Central Michigan, Northern Michigan, and the Upper Peninsula, tornadoes are rare.