The chances that a tornado is a F5, the highest classification for a tornado on the F-scale, is less than 0.1%.
A Tornado can occur at any time, but most often between 3pm and 9pm.
Funnel clouds usually last less than 10 minutes before dissipating with many only lasting several seconds. On rare occasions, cyclones can last for over an hour as many were reported to have done in the early 1900's.
Rotating thunderstorms called mesocyclones (or supercells) are the best predictors of tornado activity. Mesocyclones are well defined thunderstorms on radar that may include hail, severe winds, lightning and flash floods.
Texas gets hit with the most tornados every year. They average about 125 tornadoes every year. Oklahoma comes in next with about 57 tornadoes per year, with Kansas and Florida following close behind with 55 each. Florida of course is much smaller, and therefore has more twisters per square mile than anywhere else.
In terms of absolute tornado counts, the United States leads the list, with an average of over 1,000 tornadoes recorded each year. A distant second is Canada, with around 100 per year.
The deadliest tornado in the United States touched down on March, 18, 1925, killing 695 people and injuring 2,027 in Missouri, Illinois and Indiana.
It is a myth that a tornado cannot pass over features like valleys, mountains, lakes and rivers. When it passes over a lake or river, a tornado becomes a waterspout.
According to a study by A.M. Best, tornadoes are responsible for 57 percent of all catastrophic losses since 1953.
Tornado strength is measured by the enhanced Fujita scale, from 0 to 5, with an F5 tornado packing 300-mph winds.