LIGHTNING SAFETY GUIDELINES
This information from www.explore-rocky.com/hiking/lightning.html has been compiled from resources from the National Lightning Safety Institute and the National Outdoor Leadership School's "Lightning Safety" publication.
How Does Lightning Strike?
Lightning strikes fast. The whole process usually takes a few milliseconds. Stepped leaders of electric current leave a cumulonimbus cloud and some leaders move toward the ground. They appear as many branches, but only 1-2 branches will reach the ground. Approximately every 50 meters a new step leaves each leader and heads in a fairly random direction.
If a leader gets 100m from the ground, positively charged streamers start rising from the closest grounded objects towards the negatively charged leader. As soon as the leader is close enough to a streamer, it shoots directly to that streamer and “blazes a trail” for a significant charge (a return stroke) to shoot from the ground to the cloud.
Most ground strikes occur immediately below a cumulonimbus cloud. Rarely, a bolt of lightning can move horizontally and strike somewhere “out of the blue” (out of the blue sky) as far as 10 miles (16km) away. These horizontal strikes are rare and unpredictable, so they shouldn’t affect our decisions. Lightning tends to hit elevated sharp terrain features like mountain tops. Lightning tends to hit tall trees in open areas, with objects twice as high receiving roughly 4X the strikes. Lightning tends to hit bushes in the desert if the bush is sticking up higher than the flat ground around it. Lightning can still hit flat ground or water, but more randomly than it hits elevated objects. Even a few less feet of height can make a difference in improving your odds of NOT being the struck object. This is why the first part of getting into the lightning position is lowering yourself down.
How Can Lightning Hurt Us?
Direct strike - A stepped leader of current connects with a streamer coming out of your body, then the return stroke passed through you or over your body's surface. The return stroke is the most significant electrical event of a lightning strike and has a typical current of 30,000 amps. (Household current is 15 amps.)
Streamer Currents - Fast, high-current pulses are launched from the tops of many elevated objects near each leader as it approaches the ground. Streamer currents, while much smaller than the return stroke current, are still large enough to cause injury or death to humans.
Ground Currents - Ground currents occur with each strike and cause roughly half of all lightning injuries. Typical lightning-to-ground strikes inject roughly 30,000 amps into the Earth. How far the current flows varies wildly since the magnitude of strike current and ground conductance varies. But the closer you are to the direct strike, the stronger the ground current.
You can MINIMIZE exposure to ground potential differences and ground currents by: keeping your feet close together, by NOT assuming a prone position, and by assuming the lightning position. These actions can help MINIMIZE the amount of ground current going through your body. We’ve always been told to sit on a insulating item such as a pack, but this action is dismissed by many experts.
"There is a great deal of wishful thinking in the outdoors community that sitting on a pack or putting down metal can reduce or eliminate lightning danger," warns Ron Holle, of the National Severe Storms Laboratory. "Unfortunately, it doesn't matter what you're sitting or lying on. The flash came from 5 to 8 miles up in the cloud and has 30,000 amps, so it will penetrate absolutely anything."
Surface Arcs - High current surface arcs appear to be associated with some fraction of all cloud-to-ground discharges, during the return stroke. They appear in photographs as bright arcs of light radiating from a strike point like spokes of a wheel, in the air just above the ground’s surface. These long, hot horizontal currents have been measured up to 20 meters in length and may get longer. If you are in the path of a surface arc you are likely to conduct some of the surface arc current through or over your body. Since surface arcs emanate from the base of trees struck by lightning, never seek shelter near a tree.
Other forms of lightning damage can include: Radiation – the visible, infrared and ultra–violet radiation near the strike point, which can damage your vision. A thunder pulse can damage hearing temporarily or even permanently. During any stage of a thunderstorm, the electrostatic field can be enhanced enough around grounded objects to cause brush or point discharge (a corona). At night, you may be able to see corona as a faint glow from sharp rock outcrops or the tops of bushes or trees. You may hear corona as a sizzling or buzzing sound. Even if you can't see or hear corona, you might smell ozone, one of the chemical products of point discharge in air. If you feel hairs on your head, legs or arms tingling and standing on end, you are in an extremely high electric field.
The response to any of these signs should be to instantly (seconds matter) drop and move away from all packs, remove metal shoe fittings, spread out, and adopt the lightning position. Do not ignore these signs and do not try to run to safety, unless safety is literally seconds away. If any of these signs are detected, the probability of a close discharge is high and every effort should be made to minimize injuries and the number of injured.
How Can We Reduce Lightning Risk In The Backcountry?
There are things you can do to reduce risk during a thunderstorm, but you can never get as safe as you could be in town. Some risk reduction factors, like taking off a metallic belt buckle, might reduce burns but have little to do with avoiding becoming a fatality. But there are five actions that can reduce your risk:
1. Time visits to high-risk areas with weather patterns
2. Find safer terrain if you hear thunder
3. Avoid trees
4. Avoid long conductors
5. Get in the lightning position
Timing activities with safe weather requires knowledge of local weather patterns. You need to set turnaround times that will get you off of exposed terrain before storms hit. Begin your turnaround if you hear thunder (which means lightning is one to ten miles away.) In calm air, you can hear thunder for about ten miles. In turbulent air, you can hear the thunder for about five miles. In a driving storm, you may only hear it out to one mile. Some parties in rain storms have been struck before they heard any thunder at all.
Safer terrain in the backcountry can decrease your chances of being struck. High pointed terrain attracts lightning to the high points, and even to the terrain around it. Avoid peaks, ridges, and significantly higher ground during an electrical storm. If you have a choice, descend a mountain on the side that has no clouds over it, since strikes will be rare on that side until the clouds move over it. Once you get down to low rolling terrain, strikes are so random you shouldn’t worry about terrain as much. If you are exposed to lightning, you need to get in the lightning position as soon as possible, which obviously means you stop moving to safer terrain at that point. Many people have died while upright and walking to safer terrain, but no one has died while stopped in the lightning position. Move to safer terrain as soon as you hear thunder, not when the storm is upon you.
In gently rolling hills, the lower flat areas are probably not safer than the higher flat areas because none of the gentle terrain attracts leaders. Strikes are random in this terrain. Look for a dry ravine or other significant depression to reduce risk. Wide open ground offers high exposure during an electrical storm. Avoid trees and bushes that raise above the others, since the highest objects around tend to generate streamers. Your best bet is to look for an obvious ravine or depression before the storm hits, but when the cloud is over you, spread out your group at 50’ intervals to reduce multiple injuries and assume the lightning position.
Naturally wet ground, like damp ground next to a stream, isn’t any more dangerous than dry ground, so don’t worry about this. It used to be said that wet ground was more dangerous, because it conducted more ground current, but wet ground actually dissipates ground current faster. Neither wet nor dry is considered more dangerous than the other. Standing in water should be avoided. Dry snow is an insulator, but wet snow is a conductor. This should make travel on dry snow safer than on bare ground, because it will be harder for a person to generate streamers or conduct ground current. Avoid cave entrances. Small overhangs can allow arcs to cross the gap. Natural caves that go well into the ground can be struck, either via the entrance or through the ground. You should never be anywhere near any metal handrail, wire or cable during a storm. Avoid trees because they are taller than their surroundings. Tall trees are especially adept at generating streamers that attract strikes. If you need to move through a forest while seeking safer terrain, stay away from the tree trunks as you move. You should also avoid open areas that are 100m wide or wider. Lone trees are especially dangerous: the laws of probability say you are hundreds of times safer in a forest with hundreds of trees than you are near a lone tree in an open space.
“Cone of protection” from trees and cliffs is an arguable concept and has no place in lightning safety education anymore.
Lightning has been photographed striking 100 meters from 200 meter towers, and surface arcs have been photographed exactly where “cones of protection” inferred we were all safe.
Assume the Lightning Position when at risk. This will reduce the chances of getting a direct strike and it may reduce the other effects of lightning, but it offers no guarantees. The data says that no one in this position has ever been hurt. This position includes squatting (or sitting) and balling up so you are as low as possible without getting prone. Wrap your arms around your legs, both to offer a safer path than your torso for electrons to flow from the ground, and to add enough comfort that you will choose to hold the position longer. Close your eyes. While the prone position is lower, being spread out increases potential for ground current to flow through or across you. Keep your feet together so you don’t create potential for current to flow in one foot and out the other. Don’t touch metallic objects like ice axes, crampons, tent poles or even jewelry. You won’t get a warning that a strike is imminent because the lightning event from cloud to ground and back occurs faster than you can blink an eye, so stay in the lightning position until the storm passes. This position reduces the chances of lightning injuring you as badly as if you were standing, but is no substitute for getting to safer terrain if it is immediately available. A dangerously close strike actually offers a moment of opportunity to move, while the electrical field rebuilds itself. But in wide open country or gentle rolling terrain there are no simple terrain advantages, so use this position to reduce exposure. If you are concerned enough to use the lightning position, have your group dispersed at least 50’ apart to reduce the chances of multiple injuries.
Don’t rely completely on nifty sayings like “Up high by noon, down low by two.” Use such suggestions in planning your hikes. Lightning can strike at any time of the day. The National Lightning Safety Institute reports that most injuries occur in the summer months between 11:00 am and 9:00 pm. Plan on hiking back down the trail before the afternoon rolls around, and even earlier when hiking in the tundra. As you’re hiking, look up at the skies every 15 minutes and know how to read the ever-changing weather conditions. Again, if you hear thunder and are above treeline, turn back immediately. If you see dark clouds with flat bottoms developing, it’s a good sign that thunderstorms will develop and it’s time to head home. Stay alive and come back to hike the trail another day.
If someone in your hiking party is struck by lightning and is not breathing, you should immediately attempt to restore life by giving CPR. Their bodies do not retain the electrical charge and are safe to handle, and most people can survive a strike if given proper treatment right away. Send someone in your party to get help right away. Have one person stay with the victim until help arrives. Keep victims awake and hydrated, and make sure he/she urinates frequently. Conscious victims with injuries will probably survive, but all should have a thorough medical examination.
Some Web Sources for Lightning information: