Dangerous, long-lasting heat is expected across portions of the Central and Southeast U.S. Showers and thunderstorms, some severe, may produce heavy rain and localized areas of flash flooding across parts of the Ohio/Tennessee Valleys into the Appalachians. Severe thunderstorms are possible across parts of the northern Great Plains. Fire weather conditions possible in the Great Basin. Read More >
Thunderstorm - A rain-bearing cloud that also produces lightning.
All thunderstorms are dangerous. Every thunderstorm produces lightning. In the United States, an average of 300 people are injured and 80 people are killed each year by lightning. Although most lightning victims survive, people struck by lightning often report a variety of long-term, debilitating symptoms. Other associated dangers of thunderstorms include tornadoes, strong winds, hail, and flash flooding. Flash flooding is responsible for more fatalities—more than 140 annually—than any other thunderstorm-associated hazard.
Dry thunderstorms that do not produce rain that reaches the ground are most prevalent in the western United States. Falling raindrops evaporate, but lightning can still reach the ground and can start wildfires.
Above information borrowed and edited from FEMA publication:
https://www.fema.gov/hazard/thunderstorm/index.shtm