The number of tornadoes sighted each year in the USA has tripled in the second half of the 20th century. Experts say this is because there are more people out looking for them.
Some particularly accessible tornadoes draw crowds like fireworks displays.
Chasing the tornadoes around until they pose for a good shot seems to be pushing our luck. Inspired by movie heroes, the general impression is that as long as you keep your seat belt fastened, driving through the center of a tornado can be safe, exciting and a good way to save your marriage.
A lot of tornado footage makes its way into the marketplace. People collect tornado videos.
Some of the tornado-chasers are serious scientists trying to collect information on how tornadoes are formed, so that the government can develop more sophisticated warning systems.