Every thunderstorm produces lightning and is dangerous. Lightning can travel as far as 10 miles from the rain portion of a thunderstorm. This means that if you can hear thunder, there is a chance you can be struck by lightning. If you hear thunder, you should head for safe shelter immediately.
A safe shelter would be a building with wiring and plumbing, or a car. If inside a building, avoid windows, doors, and anything that might have a path leading to the outside that conducts electricity. A car with a metal roof and sides is the second safest place to be. As with being inside a building, avoid anything that might have a path leading outside that conducts electricity. Remember, it is the metal shell that protects you, not the rubber tires.
If you get caught outside, you should try to avoid high ground, tall objects, trees, water, and metal objects. If you see lightning strike nearby, remember that you want to be the lowest point possible. Crouch down low and keep at least a few yards distance between you and any other people.
The best rule to follow for lightning safety is the 30-30 rule. When you see lightning, count the time until you hear thunder. If that time is 30 seconds or less, the thunderstorm is within 6 miles of you and is dangerous. If you can't see any lightning, hearing thunder is a good back-up rule to seek shelter. After the last lightning strike or clap of thunder, wait 30 minutes before continuing any outdoors activity. The threat of lightning still exists even after the main portion of the storm has passed.
If you see someone who has been struck by lighting, call 9-1-1.