The path a tornado takes.

Source: Commons Wikimedia
This picture shows the development of a little funnel cloud into a powerful tornado. Starting as a little tendril, the spinning cloud evolves into a catastrophic twister. Although it appears dangerous, the ensuing twister is not as big and lethal as it may be. Based on the damage that a tornado can cause to buildings and trees, the Fujita Scale’s F-Scale is used to rate the severity of tornadoes. Tornadoes are classified into five categories, ranging from F-1 to F-5, and the classification is decided by meteorologists based on aerial or ground observations of the damage.