A tornado is a fast spinning column of air, up to 500 metres wide. There is usually very low pressure at its centre and this causes the tornado to suck things up off the ground as it passes.
Tornadoes travel at speeds of around 248mph and are ranked on the Fujita scale (with F0 being the lowest wind speed and F5 being the highest).
They mostly form in the summer months during large thunderstorms. The middle part of the United States is nicknamed 'Tornado Alley' for the large amount of tornadoes created there.
To keep safe in a tornado, you should: