In order for thunderstorms to produce tornadoes, they need a few ingredients. Thunderstorms like to form when a cold front bumps into warm, moist air. When this happens (like in the image above), it pushes the warmer air above the cold air. The power of the rising air, or updraft, keeps millions of water droplets suspended in the air until they become so heavy they fall as rain. A tornado may form if the air inside the thunderstorm spins downward and touches the ground.