LIGHTNING: WHAT TO DO WHEN STORMS ARE NEAR
Lightning is a serious danger. Thus lightning safety requires a large standoff distance from thunderstorms and a long standoff time after apparent thunderstorm decay. Thunder produced by a lightning strike travels one mile (1.6 km) every five seconds. Thus, counting the number of seconds between the visible "flash" and the audible "bang" and dividing by 5, provides the distance in miles.
Employ the "30-30 Rule" to know when to seek a safer location. The "30-30 Rule" states that when you see lightning, count the time until you hear thunder. If this time is 30 seconds or less, go immediately to a safer place. If you can't see the lightning, just hearing the thunder means lightning is likely within striking range. After the storm has apparently dissipated or moved on, wait 30 minutes or more after hearing the last thunder before leaving the safer location.
The "30-30 Rule" is best suited for existing thunderstorms moving into the area. However, it cannot protect against the first lightning strike. Be alert to changes in sky conditions portending thunderstorm development directly overhead. Larger outdoor activities, with longer evacuation times, may require a longer lead-time than implied by the "30-30 Rule."
When lightning threatens, go to a safer location. Do not hesitate.
What is a safer location? The safest place commonly available during a lightning storm is a large, fully enclosed, substantially constructed building, e.g. your typical house, school, library, or other public building. Substantial construction also implies the building has wiring and plumbing, which can conduct lightning current safely to ground. However, any metal conductor exposed to the outside must not be touched precisely because it could become a lightning conduit. Once inside, stay away from corded telephones, electrical appliances, lighting fixtures, ham radio microphones, electric sockets and plumbing. Don't watch lightning from open windows or doorways. Inner rooms are generally preferable from a safety viewpoint.
If you can't reach a substantial building, an enclosed vehicle with a solid metal roof and metal sides is a reasonable second choice. As with a building, avoid contact with conducting paths going outside. Close the windows, lean away from the door, put your hands in your lap and don't touch the steering wheel, ignition, gear shifter or radio. Convertibles, cars with fiberglass or plastic shells, and open-framed vehicles are not suitable lightning shelters.