Although tornadoes can occur anywhere in the world, most occur in the United States. The states where tornadoes most often occur ? Kansas, Nebraska, Oklahoma and Texas ? are nicknamed Tornado Alley.
A tornado is a strong rotating column of air extending from a thunderstorm to the ground. According to Weather Wiz Kids, tornadoes can produce winds up to 300 mph. They are formed when cold and warm air meet, creating instability in the atmosphere. Wind changes direction and speed, and increases in height, creating a horizontal spinning effect in the lower atmosphere. Rising air changes the rotating air from horizontal to vertical, and tornadoes can form in the area of rotation.