Except for a few fair-weather clouds, the sky looks deceptively bright and blue. Then, seemingly out of nowhere, dark clouds appear and the wind picks up.
Up here in the mountains, the weather can change quickly.
High time for hikers to start looking for shelter because all these signs point to an oncoming thunderstorm, the German Alpine Association (DAV) warns.
The seconds that pass between lightning and thunder tell you how far the storm’s center is still away. Dividing the seconds by three gives you the distance in kilometers. If the time span is 10 seconds, for example, the thunderstorm is some 3 kilometers (1.8 miles) away.
If that’s the case, hikers should urgently seek protection, ideally in a shelter with a lightning protection system.
But if there's no such refuge nearby, seeking shelter in a forest or in a hollow in an open mountain meadow is also an option. Rock caves are another alternative, but only if keeping a distance of at least 1.5 meters from the rock face is possible.
Avoid free-standing trees
Under no circumstances should hikers seek shelter close to the edge of the woods, between free-standing boulders, or under free-standing trees, according to the DAV.
It’s also not safe to stay inside a tent during a thunderstorm and any elevations or edges on the mountain should be avoided.
Conductive materials pose an additional risk. Hikers should therefore avoid water and rope-secured ascents and deposit metal equipment at some distance.
Get into a protective position
Once there’s no time to find shelter because the thunderstorm is already right above you, hikers should assume a protective position. This means squatting on an insulating surface like a dry backpack or a climbing rope with your legs closed until the storm has passed.
Ideally, of course, it shouldn't get to that point. When planning their trip, hikers should already look out for potential shelters or hill farms on the way or find a possible emergency descent.
Getting away earlier also reduces the risk of being surprised by a thunderstorm, especially if you're in a place where thunderstorms mainly occur in the afternoon.