A tornado is a narrow, violently rotating column of air that extends from a thunderstorm to the ground, the circulation of the strongest tornadoes can reach speeds of over 250 mph. Therefore, tornadoes can be among the most violent phenomena of all atmospheric storms we experience and can cause tremendous destruction that can lead to devastating consequences.

The USA has the most tornadoes in the world and some of the most destructive and deadliest.

The US has more tornadoes than anywhere else in the world, on average, around 1,200 tornadoes a year. The Great Plains in the centre of the country, on average, seeing most tornadoes, hence the area nick-named ‘Tornado Alley’. Warm and moist air from the Gulf of Mexico, dry air from Deserts of the southwest and cold air off the Rocky Mountains and Canada come together to create the perfect conditions for making severe thunderstorms in the middle of America that become powerful enough to produce so many tornadoes, sometimes destructive tornadoes.

More Info: en.wikipedia.org