A Tornado is a tube of violently spinning air that touches the ground . Wind inside the tornado spins fast, but the actual 'circle' of wind around them is huge. This makes tornadoes very dangerous. Tornadoes are especially dangerous to people in cars or mobile homes and about 60 people are killed by tornadoes every year. Tornadoes are devastating as they can cause significant injury and death. Tornadoes can tear through houses and often leave people homeless. Tornadoes can be caused by winds that have been going opposite directions with moist air meet as well as hurricanes. Nearly 3 Quarters of the worlds Tornadoes takes place in the US. Tornadoes mostly happen during strong thunderstorms called super cell storms. They cause a lot of damage to anything in their path. Tornadoes are ranked on the Fujita scale , from F0 to F5 . F0 for tornados that caused the least damage, and F5 for the ones that caused the most. Tornadoes can happen in nearly any part of the world. In the United States , a tornado has happened in all states. The middle part of the United States is nicknamed 'Tornado Alley' for the number of tornadoes there. A tornado can have wind speeds of over 300 miles per hour (480 km/ h). Most tornadoes have wind speeds less than 110 miles per hour (180 km/h), are about 250 feet (80 m) across and travel a few miles before disappearing. Other tornado- like phenomena that exist in nature include the gustnado, dust devil, fire whirls, and steam devil; downbursts are frequently confused with tornadoes, though their action is not similar.
https://www.youtube.com/watch?v=E3udFVoe95Y

The three pictures above are mode of formation