A thunderstorm is a storm with rain, wind, lightning, and sometimes hail. It happens when a big cloud, called a cumulonimbus cloud forms from warm air full of water vapor rising from the ground. The warm air makes the cloud bigger, heavier, and darker. When the cloud can no longer hold the water..... A thunderstorm happens!

Severe Thunderstorm

Severe thunderstorms are strong storms that contain winds of 58 miles per hour or faster, hail one inch in diameter or greater, and possibly contain funnel clouds or tornadoes. In the event that a severe thunderstorm is approaching, the National Weather Service will issue a Severe Thunderstorm Warning. If conditions in the atmosphere are favorable for producing a severe thunderstorm, the national weather service will issue a Severe Thunderstorm Watch.

Derecho

Edge of a Derecho - Minnesota (Public Domain image)

A derecho is a powerful, long, straight line wind storm that is part of a group of land-based severe thunderstorms. These storms are particularly dangerous because they are hard to predict, strike without warning and when they do strike, they can strike with hurricane force winds, heavy rains, flash floods, and sometimes tornadoes in a matter ot minutes. Some derechos may even have precipitation-free "eyes" like a hurricane. In 2012, a powerful derecho struck the midwestern and mid-Atlantic states, knocking out power for up to week for more than four million people. This derecho was one of America's most destructive severe weather systems in its history, resulting in the deaths of 24 people.

Great Derecho Education Video