Thunderstorms form when warm air near the ground rises. The warm air cools as it rises. A large cloud forms. Rain starts to fall towards the ground. Cool air also moves down toward the ground.
In some thunderstorms, the air moving up and down starts to spin. The spinning air can sometimes move below the clouds. A funnel cloud (a spinning column of water droplets that comes down from the base of a thunderstorm) can form when that happens.
Photo Credit: NOAA/JPL-Caltech
