Strong updrafts then pull the warm, moist air upward and create a giant vertical chimney of rotating air. Tornadoes are most likely to occur between 3 p.m. and 9 p.m., but they have been known to happen at all times of the day. Some tornadoes stay put, moving only a mile or two, while others travel more than 100 miles. Some tornadoes are almost stationary, but most move at an average speed of 30 mph while others hit 70 mph.
Tornadoes can strike in batches.
In one 24-hour period in 1974, a remarkable 148 tornadoes struck in 13 states and Canada. Violent tornadoes can last longer than an hour and have winds greater than 205 mph.