1. A tornado is a funnel-shaped cloud made up of violently rotating winds that can reach speeds of up to 300 miles per hour.
2. Tornadoes occur inside giant thunderstorms known as "supercells." These powerful storms form when warm, moist air along the ground rushes upward, meeting cooler, drier air. As the rising warm air cools, the moisture it carries condenses and forms a massive thundercloud. Sometimes these thunerclouds grow to be 50,000 feet high. Variable winds at different levels of the atmosphere feed the updraft and cause the formation of the tornado's funnel shape.
3. Tornadoes can be more deadly than hurricanes, because the rotating winds are concentrated in a small area, making them more powerful.
4. Tornadoes also cause a problem, because scientist have yet been able to give people a lot of warning as to when a tornado may be approaching.
5. Tornadoes can happen at any time of year, but most form during the spring and early summer.
6. In the United States, May and June are the peak months for the number of tornadoes. April, however, appears to be the deadliest month. An average of 27 tornado deaths have occurred during April between 1950 and 1999. One of the all-time worst tornado disasters occurred on April 3-4, 1974, when 148 twisters struck 13 states causing more than 300 deaths.
7. The diameter of a tornado can vary between a few feet and a mile.
8. Tornadoes generally travel in a northeast direction (depending on the prevailing winds) at speeds ranging from 20-60 m.p.h.
9. The conditions that lead to the formation of tornadoes are most often met in the central and southern U.S., where warm, humid air from the Gulf of Mexico collides with cool, dry air from the Rockies and Canada. This area, dubbed "tornado alley," extends from the Rocky Mountains to the Appalachians, and from Iowa and Nebraska to the Gulf of Mexico. Tornadoes can also occur through all the United States, Europe, Asia, and Australia.
10. The Fujita scale classifies tornadoes according to the damage they cause. Most tornadoes are classified as F1. An F1 tornado can cause moderate damage with winds that go from 73 to 112 miles per hour. These tornadoes can rip the roof off a house, down powerlines and cause trees to break. Only about 1 percent of tornadoes are classified as F5, causing "incredible damage." These tornadoes cause extreme damage with winds that exceed 261 miles per hour. They can destroy a town, lift a house off its foundation, and throw a car across a field.