Lightning Safety During Thunderstorms

Lightning is one of the most underestimated hazards associated with thunderstorms. South Africa records a high number of lightning related incidents each year, particularly in the interior provinces where summer storms are frequent and intense. Understanding basic safety principles can reduce the risk of injury considerably.

The Thirty Thirty Rule

A widely used guideline for judging lightning risk is to count the seconds between seeing a flash of lightning and hearing the following thunder. If that gap is thirty seconds or less, the storm is considered close enough to be dangerous, and shelter should be sought immediately. It is generally recommended to wait at least thirty minutes after the last thunderclap before resuming outdoor activities, since lightning can strike even after the heaviest rain has passed.

Seeking Appropriate Shelter

A sturdy, fully enclosed building is the safest place to be during a thunderstorm. Structures with plumbing and wiring help conduct a strike safely into the ground rather than through anyone inside. A hard topped vehicle with the windows closed is the next best option, since the metal frame directs electrical current around the occupants and into the earth. Open sided shelters, small sheds, tents and areas under isolated trees do not offer reliable protection and should be avoided.

What to Avoid Outdoors

If caught outside with no shelter nearby, there are several things worth avoiding. Open fields, hilltops and ridges increase exposure, since lightning tends to strike the highest point in an area. Bodies of water, including swimming pools and dams, should be left immediately, as water conducts electricity efficiently. Metal objects such as golf clubs, umbrellas with metal spokes, fencing and farm equipment should also be put down or avoided, since metal can attract or conduct a strike over short distances.

Groups of people caught in the open should spread out rather than huddle together. This reduces the chance that a single strike could affect multiple people at once. Crouching low to the ground, with feet together and weight on the balls of the feet, minimises the body's contact area with the ground and can reduce injury if a strike occurs nearby, though it is not a substitute for proper shelter.

Indoor Precautions

Being indoors is generally safe, but a few precautions still apply. Corded telephones and other wired electrical equipment should be avoided during a storm, since lightning can travel through wiring and phone lines. Showering, bathing or washing dishes should also be postponed, as plumbing pipes can conduct electricity. Staying away from windows and doors reduces the risk from a nearby strike, and unplugging sensitive electronics can help prevent damage from power surges.

Driving in a Storm

Heavy rain and poor visibility often accompany thunderstorms and can be as dangerous as the lightning itself. Reducing speed, increasing following distance and using headlights improve visibility and reaction time. If visibility drops sharply, pulling well off the road, away from trees and power lines, and waiting for conditions to improve is often the safest choice. Hazard lights should be used so that other drivers are aware of a stationary vehicle.

After the Storm

Once a storm has passed, it is worth checking the surroundings for fallen branches, damaged power lines or flooded low lying areas before resuming normal activity. Downed power lines in particular should never be approached, since they may still be live even after a storm has ended. Reporting such hazards to the relevant local authority helps ensure they are dealt with safely.