Tornadoes usually develop from strong thunderstorms.
A tornado often takes the shape of a funnel but it can also appear as a twisting rope. Its color can vary from grayish white to black. Tornadoes may occur any place in the United States at any time of the year. However, they happen most frequently in the midwestern, southern and central states during the months of March through September. They frequently occur between 3 and 7 p.m. but have occurred at all hours.