"Tornado Alley", as it is called, covers a large portion of the central United States. Ohio is on the far eastern edge of this imaginary bounded area, which includes real estate from the western plain states, eastward through the Mississippi Valley, to the Gulf coast, and northward into the Ohio Valley.. west of the Appalachians. This area was designated such, because the highest number of tornados typically form in this part of the country, due to a unique set up.
It's an area where cold air drops southward from Canada, and meets up with warm and moist air from the Gulf of Mexico. Dry air, due to downsloping winds on the eastern side of the Rockies also commonly gets into the mix, and when these conditions come together with an active jet stream, there is a high risk for the development of tornados.