Lightning Safety Outdoors: How to Avoid a Strike and Help a Victim

Lightning kills about 20 to 30 people a year in the United States and injures hundreds more. Most people who are struck survive, but some live with permanent damage. The best way to survive a lightning strike is not to be in its path, and the US National Weather Service sums up the strategy in five words: “When thunder roars, go indoors.”

How far lightning can reach

If you can hear thunder, you are close enough to be struck. According to NOAA, lightning can hit more than 10 miles (16 km) from the rain area of a storm, which is why people are sometimes struck under blue sky before the storm arrives or after it seems to have passed.

To judge distance, count the seconds between the flash and the thunder and divide by three for kilometres (or by five for miles). Fifteen seconds means the strike was about 5 km away. Don’t treat a long count as permission to stay out; any audible thunder is the signal to move.

Where to shelter in a thunderstorm

Only two places are truly safe:

• A substantial building with wiring and plumbing.
• An enclosed, hard-topped metal vehicle with the windows closed.

Tents, picnic shelters, small sheds, rain shelters, dugouts and open vehicles do not protect you. Once inside, keep away from corded phones, computers and other plugged-in electrical equipment, sinks, baths and showers, windows and doors, porches, and concrete floors and walls. Stay sheltered for at least 30 minutes after the last thunder.

Lightning in the mountains

Mountains are where lightning catches most outdoor people off guard. In summer, thunderstorms over high ground often build in the afternoon; in Rocky Mountain National Park, for example, storms most often form after noon. Start summit hikes and ridge climbs early, watch for towering clouds, and set a turnaround time you will keep.

If a storm catches you with no building or vehicle within reach, the NWS lists these steps. They only slightly lower the risk, so keep moving toward safety:

• Get off peaks, ridges and hilltops at once, and out of open fields.
• Never shelter under an isolated tall tree, a cliff or a rock overhang. In a forest, stay near a lower stand of trees.
• Keep away from lakes and ponds, wet ropes, and metal such as fences, poles and power lines.
• Groups should spread out, so a single strike is less likely to injure everyone.
• Don’t lie flat on the ground. If you must camp in the open, choose a low spot such as a valley.

The lightning crouch, and why it was dropped

For years, safety guides taught a “lightning crouch”: squat low to the ground and make yourself small. The illustrated guide below, from 2014, shows it. The National Weather Service stopped recommending the crouch in 2008. In its words, “the crouch simply doesn’t provide a significant level of protection”: a direct strike from overhead hits you whether you stand or squat, and believing in the crouch can tempt people to stay out too long instead of heading for shelter.

How lightning injures people, and first aid

A direct strike is the least common way to be hurt. People are more often injured by a side flash jumping from a nearby tree, or by ground current spreading out from a strike, which is thought to cause most deaths and is most dangerous to someone lying down. Indoors, most injuries come from current travelling through wiring, pipes or metal.

The main cause of death is cardiac arrest, so fast help saves lives. A person who has been struck carries no electrical charge and is safe to touch. Call the emergency number (911 in the US, 112 in Europe), start CPR if they are not breathing normally, and use an automated external defibrillator if one is available. Survivors can face long-term problems including memory loss, headaches, chronic pain and sleep difficulties, so medical follow-up matters even after a quick recovery.

See also: lightning and an enclosed vehicle; understanding a severe storm’s structure.

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• Avalanche Preparation: Training, Terrain, Equipment and Group Decisions
• An Ice Lens and the Concentration of Sunlight
• The Drinks-Can Burner: A Compact Design Demonstration

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