Lightning Precautions for Hikers: Lightning Safety in the Outdoors
Disclaimer: There are no guarantees with lightning, as unpredictable effects may occur. Travel at your own risk.
From the Lightning Laboratory -- Charge up your lightning knowledge!
Trail crews often work in alpine areas (open grassy meadows) well above the treeline. In these open meadows, workers are at risk from lightning strikes. Lightning is the #2 killer from weather, second only from drowning, more than from hurricanes and tornadoes combined. However, only 5% of those struck die. The National loss impact is $6 billion annually. One insurance claim is filed for an average of 57 strikes. In Florida, the Nation's leading lightning state, there are two measured hot spots near Tampa and Titusville, where the lightning density exceeds 10 flashes per square kilometer per year.
Lightning strikes only one victim 91% of the time, and more than one only 9% of the time. A Lightning Safety Group of the American Meteorological Society has been formed from researchers at a recent convention (see Roeder below). In populated areas, 2.4% of lightning victims are struck while talking on a corded telephone. Think of this as a miles-long, lightning-catching antenna system that is attached to your head.
An interesting photo by Krider and Ladd (1975) shows a golf green with burns in the grass radiating from the hole flagpole. These burns are about two to four inches wide, and show travel of perhaps thirty feet before the current dissipated enough to no longer kill the grass. Near a primary lightning strike, sympathetic streamers may form, rising upwards some 30 feet but not connected with the strike. If one rises from your head ....
Lightning doesn't always strike the highest point. A photo of the Mt. Lemon strike near Tucson AZ shows a side strike to the mountain far down from the peak. I have witnessed this effect near Wind River Peak WY, where a strike bypassed a rounded 1000 foot-high peak to hit a pine tree several hundred feet down the side of the rocky slope. The tree burst into impressive yellow flame.
In high mountain passes, there is little shelter, and the best precaution is the rapid descent to a lower, heavily treed forest. Within a heavily forested area, there are many trees that spread the risk of a lightning strike near you. Strikes are erratic and a matter of chance.
Dodging Lightning Dangers
I recommend a position crouching with your feet touching each other and your arms wrapped tight to your legs. Avoid contact between hands and ground, but place your palms over your ears to prevent deafness. In forested areas, stay at least 8 ft away from the trunk of an average height tree. Do not stand near a tall tree that projects above its companions.
After lightning current flows down a tree, it dissipates through the roots and wet soil. This current is closer to the surface if the soil is dry except in the top rain-soaked area, which may be only a few inches thick. In these conditions, the current flow is concentrated in perhaps the top six inches of soil. As it flows away from the tree, there is a voltage drop across the wet soil. Cattle and horses are especially likely to be shocked, as their hooves are far apart. So by keeping our feet together, we limit the voltage difference that might cause current to flow up one foot and down the other. The risk of taking a strike to the head or shoulder is reduced by crouching with head low.
Members of a party should stay separated by at least twenty feet, as if one person is struck, the others will likely survive, and can then provide CPR for the struck person. This is about the only time that CPR in the wilderness is worth doing, as it is impractical do CPR for several hours. Lightning strike victims have a very good chance of resuscitation when they are immediately given CPR, but recovery is unlikely if not occurring within twenty minutes. Oxygen to the brain quickly falls, and in four to six minutes without CPR, brain death will occur. The victims are not electrically charged; after all, they are lying on the ground, and the lightning stroke has stopped. Since they usually will not have broken bones or severe trauma, they can be removed from dangerous locations prior to continuing CPR. Perform at least one CPR cycle first.
An obvious warning is when the electrical field strength in the air is so high that your hair stands on end. In a memorable videotape, some three smiling hikers were standing there with their hair rising, and a moment later, one were struck and killed by lightning. A nondestructive test of this is to put your arm near your TV screen. Do this so you know what it feels like. You will feel the hairs being attracted to the screen. If you should feel a similar effect on a mountain peak, it's time to run fast but carefully to lower elevation and protection.
The Lightning Safety Group suggests a 30/30 rule. If you hear thunder 30 seconds after the flash, seek shelter, and stay there until thirty minutes after the last thunder is heard. Late strokes might strike someone who prematurely leaves shelter. Strikes have hit some 56 miles from a storm, thus awareness of weather conditions is important to be prepared to take action. In groups, someone should be appointed as a weather watcher to ensure that someone is really paying attention. I suggest someone who is really concerned be selected to be the lookout. They will be attentive, and need only be "empowered" to be truly effective in alerting the others.
Your group must be especially aware of incoming weather. I teach my trail crew to check the weather direction every ten minutes or so, looking at the direction that the lowest clouds are coming from. With mountains around us blocking distant views, a storm can quickly appear over the ridge. The first day, I tell them at breakfast there will be a test, and they must immediately point to the weather direction and keep pointing the way that they first point. On the trail with work in progress, I shout "Where's the weather direction?" The diversity of guesses is astounding, and for the rest of the trip, they become more aware of the weather. Special thanks to Mr. William Roeder of the PAFB Weather Squadron for providing additional information.
Frequently Asked Questions
Here are the Lightning Quiz Answers:
by Frank R. Leslie, updated 02/12/2004 14:23
Return to Renewable Energy Quick Links for Students