Lightning

Lightning kills around 20 people a year in the United States and injures many more, according to the National Weather Service. Most of those deaths happen outdoors, often in conditions where the storm was forecast and the warning signs were visible well before the strike. Lightning is one of the most dangerous and at the same time most preventable hazards in the mountains. The reason people still get struck has very little to do with knowledge and almost everything to do with timing decisions made on the way up, when the weather still looks fine and the summit still looks close. By the time you can see the storm clearly, the decision that would have kept you safe was made hours ago.

This article covers what lightning actually does to people, how to read the sky and the clock to stay ahead of it, what to do if you are caught in exposed terrain, and what first aid looks like for someone who has been struck. The information is standard. The discipline to act on it before you have to is the part that takes practice.

How Lightning Actually Hurts You

Direct strikes are the dramatic version and they account for a minority of lightning injuries in the backcountry. Most lightning casualties happen through one of four indirect mechanisms, and understanding the difference shapes the response.

Direct strike. The bolt hits you. Most lethal version, but relatively uncommon if you avoid being the tallest object around.

Side flash. The bolt hits something near you — a tree, a rock outcrop, a metal post — and a portion of the current jumps to you. This is why "sheltering under a tree" is the canonical wrong move.

Ground current. The bolt hits the ground and the charge spreads outward through the earth in waves. If your feet are far enough apart, the voltage difference between them drives current up one leg and down the other. This is responsible for a significant share of lightning casualties, including most multi-victim incidents.

Contact injury. You are touching something that gets struck or that conducts current to you — a metal fence, a hiking pole planted in wet ground, a tent pole, a wet rope, plumbing in a backcountry hut.

Blunt trauma. The strike or the shockwave throws you, or causes a fall. Lightning has killed people who survived the electrical injury but fell off what they were standing on at the moment of the strike.

Lightning can strike well outside the visible storm — the so-called "bolt from the blue" can travel ten miles or more from the parent cloud. If you can hear thunder, you are within strike range, even if the sky directly overhead looks clear. That fact alone reshapes most people's mental model of what "the storm is too far away" means.

Read the Sky, Read the Time

The most useful piece of lightning prevention in mountain country is not weather knowledge. It is the clock. Afternoon thunderstorms are predictable enough in summer mountain weather that you can plan around them. The standard rule in the Rockies, the Sierra, the Cascades, and most western ranges: be off the summit by noon, off exposed terrain by early afternoon. The storms build through the morning on warm days, peak between 1pm and 5pm, and break down through the evening. Plans that have you on a ridge at 2pm in July are not bold plans. They are bad plans.

Watch the clouds. Cumulus clouds that grow vertically through the morning — going from flat-bottomed puffs to tall, building columns — are the warning sign. When the tops start to flatten into the anvil shape, the storm is mature and you are too late to be making careful decisions. The bases will darken before the storm reaches you. The wind direction may shift. The temperature may drop suddenly. Any of those is a signal to move.

The 30/30 rule is widely taught and worth remembering. If you see a flash and the thunder follows within 30 seconds, the storm is within six miles and you are in striking range. NOAA's lightning safety guidance recommends waiting at least 30 minutes after the last audible thunder before resuming exposed-terrain travel. The risk does not drop to zero the moment the storm passes — trailing strikes from the back edge of the system kill people who thought they were clear.

Cell-phone radar apps help, but with caveats. Coverage in the backcountry is spotty, the data is delayed by minutes, and small mountain cells can form faster than the radar picks them up. Use the radar to confirm what your eyes are already telling you, not as your primary detection system.

When You Are Caught Out

The single most important thing is to get off the most exposed terrain you are on, in the time you have. The hierarchy of bad places to be, roughly worst to least-worst:

• Summits, ridges, and peaks — anywhere you are the tallest thing.
• Open meadows, frozen lakes, talus fields where you are isolated and elevated above the surrounding terrain.
• Under lone trees, lone outcroppings, or any single tall object in otherwise open ground.
• At the base of cliffs and rock walls (side flash risk).
• On or near water — lakes, streams, wet rock surfaces that conduct ground current.
• In contact with long metal objects — fences, climbing gear stretched out, antennas, rebar.

The better places, also roughly best to worst:

• Inside a sturdy building, if one is accessible.
• Inside a hard-topped vehicle (the metal cage is what protects you, not the rubber tires).
• In a dense, uniform stand of trees of similar height, away from the tallest ones — not under the tallest tree, but among trees that are all roughly the same height as their neighbors.
• In a depression or low spot in the terrain — a gully (not a stream channel), the lee side of a slope, anywhere below the ridgeline.
• In a tent or improvised shelter only as a last resort. Tents are not protective. The common belief that they are is one of the more dangerous myths in backcountry lightning safety.

Spread out as a group. Standard guidance is to keep at least 20 feet between people, ideally more. The reason is ground current — a single strike can injure multiple people clustered together when it would have hit only one of a spread-out group. Spreading out also means a survivable incident does not become a multi-casualty one.

Get rid of metal contact and elevated objects. Set hiking poles, ice axes, and crampons aside. Take metal-frame packs off if you are wearing one. Move at least a body length away from the gear pile so a strike on the metal does not arc to you.

Insulate from the ground if you can. A foam sleeping pad under your feet, or crouched on top of a pack, gives some protection against ground current. It is not a guarantee, but it is one of the few things that does measurably help in exposed terrain.

The Lightning Crouch Question

For decades, the standard advice for someone caught in exposed terrain with no better option was the "lightning crouch" — squat on the balls of your feet, feet close together, head down, hands over your ears. Current Wilderness Medical Society guidance still includes the lightning position as a recommendation when no safer shelter is available, but assigns it a low evidence grade and treats it as a last resort rather than a primary protective measure. The reasoning is that the position is physically exhausting and cannot be held for long, and it tends to give false confidence to people who use it as a substitute for the much higher-value decisions about where to be and when.

The honest version: getting to safer terrain matters far more than your posture once you are there. If you are stuck in genuinely exposed terrain with an active storm overhead and no better option, minimizing your footprint — feet close together, low to the ground, ideally insulated from it — is better than standing up. But the lightning crouch is not a strategy. It is a last resort, and the strategy is being somewhere else when the storm arrives.

After a Strike: First Aid

Lightning injuries are unusual among electrical injuries in a few specific ways, and the differences shape the response.

Lightning victims do not carry residual charge. You can and should touch them immediately. The common fear that a struck person is "still electrified" is wrong. Treat them like any other patient.

Cardiac arrest is the leading cause of death, and it responds well to CPR. Lightning often causes the heart to stop in a rhythm that responds to chest compressions far better than typical cardiac arrest. The longer a victim has been down, the lower the odds — but lightning victims have walked away from cardiac arrest after extended CPR more often than other arrest causes.

Reverse triage applies. In a multi-victim lightning strike, the standard first-aid priority is reversed. Apparently dead victims get treated first, because cardiac arrest from lightning is potentially reversible with immediate CPR, while breathing victims will usually be okay for the few minutes it takes to address the unresponsive ones. This is the opposite of how triage works in almost every other situation.

Other injuries to watch for: burns (often patterned, sometimes where metal jewelry or zippers were in contact), eardrum rupture, neurological effects (confusion, memory loss, temporary paralysis), and blunt trauma from being thrown by the strike. Always evacuate a lightning victim, even if they appear uninjured. Delayed cardiac and neurological effects are real and can appear hours later.

Special Situations

On water. Get to shore. Water is a conductor and an open lake or river puts you above the surface plane. If you cannot get to shore, get as low as possible in the boat, away from metal, and stay there until the storm passes.

In a vehicle. Generally safe. The protection comes from the metal cage of the body, not the rubber tires — charge flows around the outside of the vehicle to the ground. Convertibles, open Jeeps, ATVs, and motorcycles do not offer this protection. Roll the windows up. Avoid touching metal parts of the interior during the storm.

In a tent. Get out if you can reach better shelter. Tents do not protect against lightning. Aluminum poles, wet fabric, and stakes driven into ground all conduct current. If you absolutely cannot move — you are in extreme weather, far from alternatives, in the dark — insulate from the ground with your sleeping pad and spread out from other tents.

In a slot canyon. Lightning is rarely the primary danger in slot canyon weather — flash flooding is. A storm anywhere in the drainage above you can fill the canyon with no warning. If you hear thunder while in a slot, your priority is reaching higher ground, not lightning posture.

When You Are Safe Again

Wait at least 30 minutes after the last audible thunder before returning to exposed terrain. The back edge of a thunderstorm system can still produce strikes, and "the rain stopped" is not the same as "the storm is gone." Use the time to dry out, eat something, and reassess the rest of the day. A close call with lightning is also a signal to look honestly at the day's plan — if you got caught out this time, was it bad luck or a planning gap that will catch you again next time?

Related Resources

For the gear, planning, and trip-timing habits that prevent most lightning exposure in the first place, see Wilderness Preparedness. For CPR and wilderness first aid training to prepare for a strike response, see First Aid & Wilderness Medicine. For real-time storm tracking tools and the limits of forecasting in mountain terrain, see the Weather section. For the full WMS clinical practice guidelines covering lightning epidemiology, prevention, and treatment in detail, see the 2014 WMS Lightning Injury Guidelines.