Thunderstorms in the mountains: correct behavior

Being surprised by a thunderstorm during a multi-pitch climbing tour can quickly lead to dangerous situations. In this article you will learn how to recognize approaching thunderstorms, what to do when the weather changes, and where to find shelter in the mountains.

A contribution in cooperation with Bächli Bergsport

In the Alps, strong thunderstorms during the summer months are among the most unpleasant and also frequent objective dangers on the mountain. Side effects such as wetness, cold, falling rocks, icing or lightning can quickly provoke dangerous situations. Below you will find important tips on how to behave properly during thunderstorms in the mountains.

Thunderstorms in the mountains: the overview

What needs to be taken into account when planning a tour?

As with other objective dangers in mountain sports, the principle of planning the tour in such a way that you don't get into the situation in the first place also applies to thunderstorms. Of course, this is easier said than done. Nevertheless, today's weather forecasts and models are so accurate that they form an important basis for decision-making in the run-up to the tour.

Since short-term forecasts are more meaningful than medium-term forecasts, it is worth making decisions as quickly as possible based on the latest weather report. Weather reports specially tailored to the mountains, such as the Alpine weather report or the DAV mountain weather report, can also be helpful.

It is definitely worth leaving early in the summer months, as many thunderstorms are caused by the daytime sunshine and storms often only form in the midday or afternoon.

Earlier start, more reserves, more safety: If there is a risk of thunderstorms, it is worth starting the mountain tour early.
Earlier start, more reserves, more safety: If there is a risk of thunderstorms, it is worth starting the mountain tour early.

What is the difference between thermal thunderstorms and frontal thunderstorms?

Thermal thunderstorms – i.e. those local thunderstorms that occur when the air near the ground warms up due to solar radiation and subsequently rises – are difficult for meteorologists to predict. Heat thunderstorms are a frequent weather phenomenon, especially in the hot months. The fact that they are often small-scale and local is reflected in the accuracy with which they can be predicted.

hardshell jackets
When the weather changes, it can quickly get cold. Bächli Bergsport offers a wide range of hard shell jackets that reliably protect against rain and wind.

In contrast to warm thunderstorms, weather reports can predict frontal thunderstorms with a high level of accuracy. Frontal thunderstorms are possible at any time of the year or day. They form at the front of cold fronts and are associated with a sudden change in the weather, which can be massive, especially in the high mountains.

It is therefore not advisable to sit out a front thunderstorm. Rather, you should plan the tour according to the weather forecast and shorten it if necessary, so that you are back at the starting point in time.

Cumulonimbus clouds herald weather changes. Frontal thunderstorms move, most often to the east. Thermal thunderstorms are usually relatively stationary. Image: Martin Vysoudil
Cumulonimbus clouds herald weather changes. Frontal thunderstorms move, most often to the east. Thermal thunderstorms are usually relatively stationary. Image: Martin Vysoudil

What signs announce a change in the weather?

Since the exact course of the weather cannot be predicted with 100 percent certainty, it is important for rolling tour planning to keep an eye out for changes or possible weather signs in addition to the weather report.

  • A possible indicator of a change in weather can be cumulonimbus clouds. These storm clouds stretch high into the sky like cauliflowers and grow out in the shape of an anvil at the upper edge of the cloud.
  • Cirrus clouds with a wall of clouds behind them indicate a cold front that is approaching.
  • If a halo forms around the sun or moon, i.e. a ring-shaped light effect, the mountain air is more humid. Accordingly, a slower deterioration in the weather can be assumed.
  • Another sign of humid mountain air and a possible deterioration in the weather are contrails from airplanes that remain visible in the sky for a long time.
  • If the altimeter shows an increase even though you are not moving, the air pressure is falling, which is equivalent to a deterioration in the weather.
  • Acute warning signs for an approaching thunderstorm are gusty, freshening wind or electrical charges (buzzing) in the air
If you climb without moving, this indicates falling air pressure and a deterioration in the weather. Image: Photo by Lukas on Unsplash
If you climb without moving, this indicates falling air pressure and a deterioration in the weather. Image: Photo by Lukas on Unsplash

How do I behave in the event of a thunderstorm?

If you are surprised by a thunderstorm despite serious tour planning, the following rules of conduct can help to improve your situation.

  • Leave particularly endangered places such as exposed ridges, peaks or rock towers as quickly as possible.
  • If you are no longer able to find a safe place such as a mountain hut or a bivouac box with a lightning rod, you are largely protected from direct lightning strikes even in large caves or within an isosceles triangle under rock faces.
  • To avoid step tension and to avoid provoking a direct impact, it is best to crouch down on a backpack or a dry rope with your knees leaning tightly
  • In terrain where there is a risk of falling, it is advisable to belay yourself and wear a helmet, especially since the electric shock of a lightning bolt can literally throw you away.
  • Metallic objects such as pickaxes, crampons or carabiners do not attract lightning, but they are good conductors. So keep them away from your body and, if possible, store them a few meters away.
Modern sports watches are not only helpful when it comes to keeping track of time. Features such as an altimeter can help to identify weather changes at an early stage.
Modern sports watches are not only helpful when it comes to keeping track of time. Features such as an altimeter can help to identify weather changes at an early stage.

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About Bächli mountain sports

Bächli mountain sports is the leading Swiss specialist shop for climbing, mountaineering, expeditions, hiking, ski touring and snowshoeing. At currently 13 locations in Switzerland, Bächli Bergsport offers its customers expert advice and high-quality service. Published on LACRUX Bächli mountain sports periodically exciting contributions to the topics climbing, bouldering and mountaineering.

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Credits: Cover photo by Levi Guzman

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