Tornadoes happen in almost all over the world. This evaluation report will be limited to the tornadoes in the United States of America. Some states that suffered it very badly and some facts and figures supporting it. Tornadoes have hit all 50 U.S. states. But this doesn't happen every year. The 30-year average number of tornadoes per year in Alaska, Rhode Island and Vermont is closer to zero than to one. In Oklahoma and Texas, the average jumps to 52 and 126, respectively, though the high number in Texas is mainly due to the state's size. To account for the different sizes of states, tornado averages for the USA are compared by looking at the annual number per 10,000 square miles — an around about the size of Vermont. For example, Oklahoma is about 70,000 square miles, or about seven Vermonts. If the entire state averages 52 tornadoes every year, then the number per year per 10,000 square miles is 52 divided by seven, which equals a little more than seven. While no state is immune to a twister's violent winds, there are places where they touch down more often. The highest concentration of tornadoes is in Oklahoma and Texas, and in Florida. Frequent thunderstorms in western Florida contribute significantly to the number of twisters. Most Florida tornadoes, however, are weak. Fewer thunderstorms rumble across the Plains each year, but the storms form in an area where the chance for tornadoes is higher in the spring and early summer because the conditions for tornadoes are more favorable. In fact, the geography of this part of the central USA favors the development of the largest and most dangerous tornadoes, earning it the name "Tornado Alley."