Seek shelter indoors when a storm is overhead. This greatly reduces lightning exposure risk.
But it's both before and after the brunt of the storm where people are most often caught unaware and are struck by a "bolt from the blue.”
The 30/30 Rule -
- When you see lightning, count the time until you hear the associated thunder, and if this time delay is 30 seconds or less, go immediately to a safe location as described above. The lightning casualty statistics are full of stories where persons who were just about to make it to safety, when they were struck. Even a few extra minutes lead time can be lifesaving.
- If you cannot see the lightning, just hearing the thunder means you are most likely to already be within striking range, and it is time to seek appropriate shelter.
- After the storm conditions have apparently dissipated or moved on, wait a further 30 minutes, after hearing the last thunder clap before leaving the safe area. Should thunder be heard yet again within this period, begin the recount from the last thunder heard.
- The “30–30 Rule” is best suited for existing thunderstorms moving into the area. However, it cannot predict or protect against a first lightning strike. Thunderstorms can develop overhead where there will be no prior notice that a storm is incoming. Be alert to changes in sky conditions portending thunderstorm development directly overhead. See if Cumulous clouds have formed overhead.
Safest actions during an active event -
- Avoid contact with corded phones and devices including those currently plugged into electric for recharging. Cordless and wireless phones not connected to wall outlets are OK to use.
- Avoid contact with electrical equipment or cords. Unplug appliances and other electrical items such as computers and turn off air conditioners BEFORE the storm arrives; not during it. Power surges from lightning can cause serious damage.
- Only use battery-operated radios for updates from local officials.
- Avoid contact with plumbing, washer/\dryer or electrical conduit. Do not use the sink or shower.
- Indoors, stay away from windows and doors, and stay off porches and catwalks.
- Do not lie on concrete floors and do not lean against concrete walls.
- Avoid natural lightning rods such as a tall, isolated tree in an open area.
- Avoid hilltops, open fields, the beach, a boat on the water or water ponds, lakes, rivers, streams, etc…
- Take shelter in a sturdy building. Avoid isolated sheds or other small structures in open areas.
- Avoid contact with anything metal—tractors, farm equipment, motorcycles, golf carts, golf clubs, and bicycles.
- If you are driving, try to safely exit the roadway and park. Stay in the vehicle and turn on the emergency flashers until the heavy rain ends. Avoid touching metal or other surfaces that conduct electricity in and outside the vehicle.
Alternatively if the safest action is not possible, do these –
- If the thunderstorm is above you (flash-to-thunder time less than 5 seconds) and you are not able to take the action suggested above, then all you can do is minimize the risk of being struck, or affected by the indirect effects of lightning. You should:
- Seek a depressed area; avoid high places
- Keep away from large isolated trees; (however, some protection is afforded in a forest if care is taken not to touch or stand too close to any particular tree)
- If in a group, stand at least 15 feet apart.
- If hopelessly isolated in an exposed area and your hair stands on end, assume a crouched position with your feet together, or squat with your feet tucked in close to your body. The hair static is indicative that the e-fields at ground level are rising very fast, and that lightning is about to strike.
Read more: http://www.lightningsafety.noaa.gov/