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Friend and I had this discussion, and came to no conclusion:

Hiking in the mountains. Crossing a range through a pass. Peaks on either side are a good thousand feet higher. Are you at serious risk of getting hit by lighting?

More generally: If you are walking a ridge line, and see a storm developing, how far below the ridge line do you need to be to be reasonably safe?


Edit:

Since asking this question I've been doing more reading. Unless the the mountain is sharply above you -- better than 45 degrees, you only have a very moderate amount of protection. 45 degrees is steeper than the angle of repose -- 37 degrees -- the angle you can stack loose rock and not have a slide.

So the 'best answer' is correct. There is no safe path.

Still: only about 15-20 people a year die from lighting strikes, mostly fishermen. So the real question becomes: How big is the whole risk?

While strikes 6-10 miles away from the base of the thunderstorm have occurred, most of the ground strikes are under or very close to the edges of the storm base.

If we take the LD50 radius of a lightning strike at 50m then it requires a storm with 133 strikes per square kilometer to land one near you. A storm with a 10 km diameter would need to deliver about 10,000 strikes. to zot a person under it's immediate footprint. That's several hours at one per second. The storms I have experienced in the mountains are both shorter than that, and seem to be limited to a few strikes per minute.

Net conclusion: Avoid the really high risk places, and enjoy the show. Overall moving toward safety is better than staying put.

I've been unable to find stats on how much higher your risk is standing vs the lightning position (squat in a ball)

Overall on a per trip basis, I would rank risks largest to smallest:

  • Accident traveling to the hike
  • Avalanche (low 30's per year, North America)
  • Climbing accidents (low 20's per year, North America)
  • Lightning (mid to high teens per year, US)
  • Wildlife attack (a few per year)

This doesn't take into account the relative frequency of the activity. Fishermen have a higher rate because they are willing to fish in the rain. And there are a lot more skiers and snowmobilers at risk of avalanche than of people walking the high country, or doing technical rock climbing.

  • Sherwood, I apologize for a comment link instead of an answer. I came across something that might be helpful, but I'm not a hiker so I don't know enough about what you do. The Colorado High Peaks are more dangerous than many areas when it comes to lightning storms. This lightning strategy from PeakMind might be helpful. Be careful! – Sue Saddest Farewell TGO GL Jul 31 '18 at 21:07
  • @Sue The link is good enough you should redo your comment as an answer. Correct, it is not complete, but it is a good outline of the various risk factors, and should be of interest to anyone who finds my original question. Thanks. – Sherwood Botsford Aug 1 '18 at 0:13
7

The pass is safer than the peaks on either side of it, but less safe than not hiking over the pass.

When I did my Instructors course for Summit Adventure, hiking over a pass during a thunderstorm would have been considered extremely unwise, and the procedure would have been to either not cross or to get the heck off if you were on top and saw a storm coming.

When I did the Uinta highline trail last summer, there was basically a pass to cross every day, and plenty of thunderstorms. I just waited the storms out in the valley below rather than risk it.

You want to have enough leaway in your planning that you don't have to cross the pass right then and there.

Same for ridgelines, you want to be heading down if a thunderstorm rolls in.

As for estimating what taller points are more likely to be hit, there is a What If XKCD on the subject.

  • Good answer. You get a point. I agree about ridgelines. Question is, how far down? 1 km (vertical) is definately sufficient. Is 200m? Passes: Have you seen a strike in a pass? I worked at Philmont Scout ranch one summer. The ridgeline was 1/2 mi away horizontally and 200 feet above us. Almost daily thunderstorms would strike on the ridge behind us, but never in the valley. – Sherwood Botsford Aug 1 '18 at 0:23
  • @SherwoodBotsford, there is no "definitely safe" distance down. High points only provide local lightning protection -- when the lightning leader is about to hit the ground, it'll hit the highest point within a hundred feet or so. If the high point is further away than that, it'll provide no effective protection. – Mark Aug 1 '18 at 2:40
  • Getting below the tree line is generally a good idea, and not just for lightning - I've been in thunderstorms with big enough hail that I would not want to be out in the open. – Jon Custer Aug 2 '18 at 15:25

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