You’re three pitches up the Great White Book on Stately Pleasure Dome at Yosemite’s Tuolumne Meadows. It's a warm sunny morning. You're having lots of fun. Your partner is chimneying up the wide flake above your belay. You look down valley toward Half Dome and see a thunderstorm building over Glacier Point. Is it coming your way? You see a distant lightning flash. What do you do?
The first thing to do is to be proactive — do something. You have to get off the cliff because you know you don't want to be on top of the dome if the storm hits. Follow these 8 tips to avoid being caught in a lightning storm.
1. Check the weather forecast before going out.
Photograph © Thomas Allen/Getty ImagesA simple thing like checking the morning or the extended forecast makes you aware that possible storm and lightning problems could arise during your outing. If there is a chance of severe storms, change your plans accordingly. If you’re on a road trip, a weather radio keeps you up-to-date on changing conditions and forecasts.
2. Do your climbing in the morning before it storms.
Be aware that severe storms usually build up by early afternoon, after the morning sun heats the air. Get an early start; descend from mountain summits and ridges before storms build; and be on your way down by the time the threat of lightning is greatest.3. Be prepared to change or abandon your climbing plans.
Remember that weather does not behave in normal predictable ways. Lots of moisture in the atmosphere can cause storms to build early in the day. If you see storms building, play it safe and change your plans before thunderstorms develop.4. Pay attention to atmospheric changes.
Pre-lightning indications include a crackling noise; the distinctive odor of ozone; the blue glow or corona of St. Elmo’s Fire around a person’s head; and your hair crackling, buzzing, and standing on end. If any of these symptoms occur, it’s wise to descend and take cover. Be advised that lightning also strikes without any of these prior warming signs.5. Get off high places before a storm arrives.
Any high place such as mountain summits, cliff-tops, ridges, open passes, and cliffs are dangerous and susceptible to lightning strikes.6. Learn to recognize thunderstorms that produce lightning.
Clouds that usually produce lightning have vertical development and dark anvil-shaped bases. Lightning usually coincides with rainfall, but not always. Strikes can come from almost clear skies—the literal "bolt from the blue."7. Use thunder to determine how far a storm is from you.
If you hear thunder and can see lightning, you’re under threat of being struck. Determine the distance of a strike by counting the number of seconds from when you see the flash to when you hear the thunder. Then divide the seconds by 5 to get the distance of the lightning in miles. For example: You count 10 seconds from the lightning flash to the thunder; divide 10 by 5 and you determine that the lightning is 2 miles away. 10 seconds/5 = 2 miles.8. Follow the 30-30 Rule.
The National Weather Service advocates following the 30-30 Rule to stay safe from lightning. If the time between when you see a lightning flash until you hear its thunder is less than 30 seconds, then take shelter as soon as possible. Don’t resume activities until 30 minutes after you last observe lightning and hear thunder.
