A thunderstorm is a weather event characterized by heavy rain, strong winds, and loud claps of thunder. These storms form when warm, moist air rises and cools, creating clouds filled with water droplets. When the droplets become too heavy, they fall as rain, and the rapid movement of air can create lightning, which is the bright flash seen during a storm. During a thunderstorm, you might hear the rumble of thunder as it travels through the air. This sound is caused by the rapid expansion of air heated by lightning. While thunderstorms can be exciting to watch, they can also be dangerous, so it's important to stay safe indoors when one occurs.