If you can hear thunder, you are close enough to the storm to be struck by lightning. Lightning can strike as far away as 10 miles from the area where it is raining.
If you can see lightning flashes, count the seconds after a flash until you hear thunder. If that time is 30 seconds or less, the storm is within 6 miles and is dangerous. Seek shelter immediately.
If caught in the open during a thunder and lightning storm and the hair on your head or neck begins to stand on end, go inside the nearest building immediately! If no shelter is available, crouch down immediately in the lowest possible spot and roll up in a ball with feet on the ground. Do not lie down!
If outdoors during a thunder and lightning storm, avoid water! Also avoid metal objects such as wires, fences, power tools, railroad tracks, etc. Unsafe places include: tents, golf carts, underneath trees. Avoid hilltops and open spaces. Where possible, find shelter in a building or in a fully enclosed metal vehicle, such as a car, with the windows shut.
Wait at least 30 minutes after the last clap of thunder before leaving shelter.
Don't be fooled by sunshine or blue sky! Lightning is more likely to come from the back edge of a thundercloud than from the front edge.