A tornado is a spiral of spinning wind that reaches out of the bottom of some very large thunderclouds.
The world's fiercest winds occur in tornadoes. Although they last for just a few minutes they can destroy houses and even lift cars and trains into the air.
The UK is the place with the greatest number of tornadoes for its size in the world, but UK tornadoes are small compared with those in places like the USA where thunderstorm clouds are much bigger.
