Since the center of the funnel is a low pressure area, air rushes into the column and rises. The air is cooled as it rises and water vapor condenses to form the familiar funnel shaped cloud. As the rotating winds begin to pick up dirt and debris from the ground, the funnel will darken. The strongest tornadoes occur in supercell thunderstorms which can also produce large hail and strong downbursts. Tornadoes are classified by wind speed and damage according to the Fujita Scale.
Tornadoes can occur anywhere at an time of the year.
However there are certain areas that favor tornado formation at different times of the year. In the southern states peak tornado season is March through May when warm, moist gulf air mixes with the cooler air masses that extend into the south. In the northern states the peak tornado season is in the summer, when the wdarm, moist gulf air reaches farther north. In some areas along the Gulf Coast there is a second peak season in the fall. The warnings are passed on to local radio and television stations and are broadcast over local NOAA Weather Radio stations serving the warned areas.