Tornadoes form when hot, humid air rises from the ground and meets with the cooler, denser air that is falling back to Earth. The two airstreams begin to swirl, pulling in more and more air to form a funnel-shaped cloud. The winds can swirl faster than 261 miles per hour! Newly revised and vetted by weather experts from National Oceanic and Atmospheric Association, Tornadoes is an accessible introduction to this fascinating phenomenon.