Most areas of the world can get tornadoes. However, Indiana has a realtively high incidence due to its climatic setup. It recieves some of the same influence that Tornado Alley does. The setup for the occurence of significant tornadoes usually starts when a storm system pull warm, moist air from over the Gulf of Mexico, while cooler air is pulled down from Canada. If the warm air mass is unstable enough, the collision of these two air masses will trigger thunderstorms. If the setup of wind shear is right, then these thunderstorms can start rotating, giving them the potential to produce tornadoes.