 Tornadoes or twisters are columns of dangerously fast rotating air formed from storm clouds. When the narrow end of the funnel touches ground, it becomes a tornado. This part of the funnel can be almost two miles wide. The most dangerous tornadoes have 200 mile per hour winds that can pick up and carry a house. Most are much smaller, but still dangerous. The majority of the world's tornadoes occur in the United States in an area called Tornado Alley. Tornado alerts are broadcast over radio, TV, smartphones, and with sirens. If a tornado approaches, shelter in a basement or interior room away from windows and doors.