Severe thunderstorms can pose a threat to life and property. They can produce:
- Downburst winds 60 mph or greater
- Large, destructive hail, one inch thick in diameter or greater
- Flooding rains
- Frequent cloud-to-ground lightning
Tornadoes can also be possible during severe thunderstorms.
Know what the terms mean:
- A severe thunderstorm watch means a severe thunderstorm is possible in the next few hours and you should prepare.
- A severe thunderstorm warning means a thunderstorm, capable of causing damage and injury, has been sighted or detected by radar. Go indoors and stay away from windows. Heading into the basement or the lower level is encouraged.
Additional information from the National Weather Service is available online.
The Illinois Emergency Management Agency’s Severe Weather Preparedness Guide is also available online.
By Argonne’s Office of Emergency Management