Storms are a serious hazard in hiking. They can form very quickly and catch hikers off guard. While summer is the ideal season to hit the trails, the intense heat also increases the risk of thunderstorms. It is therefore essential to know the right steps to take when a storm strikes during a hike.
How to anticipate a storm while hiking?
Before even heading out on a hike, always check the weather forecast and in particular the atmospheric instability indices. Hiking in intense heat increases the risk of thunderstorms, especially in the mid to late afternoon. An early start is therefore recommended.
Out on the terrain, several signs can help you recognise an approaching storm. First, the formation of cumulonimbus clouds. These anvil-shaped clouds are a classic warning sign. A sudden drop in temperature and a shift in wind direction, or even sudden gusts, can signal that a storm is on its way.
Signs of static electricity (hair standing on end, tingling sensations on the skin, buzzing sounds…) indicate that a lightning strike may be imminent. As soon as the gap between a flash and the thunder is less than 30 seconds, treat the storm as dangerous.
What should you do if a storm breaks out during a hike?
Adopting a safety position
In the mountains, a safe shelter is not always within reach. To minimise the risk from a lightning strike, you must adopt a safety position. To do so, crouch down with your feet together, arms wrapped around your knees and head lowered. If your rucksack is thick enough, sit on it to reduce direct contact with the ground.
Moving away from risk zones
At the first rumble of thunder, you must leave summits, ridges, cols, arêtes and open plateaus, which are particularly exposed to lightning. Also avoid metal structures (fences, pylons, via ferrata…) and stay away from bodies of water. These can conduct current after a strike.
Managing the group
During a storm on a hike, staying grouped together is a bad idea. You must spread out at least three metres apart to prevent an electrical arc from jumping between people. Each person should adopt their own safety position, while staying close enough to communicate if needed.
Managing your gear
Metal objects do not attract lightning on their own, but they can become dangerous if a strike occurs nearby. As a precaution, place your hiking poles, ice axes, metal-framed pack or any other equipment 20 to 30 metres away from you.
Common traps and bad ideas to avoid
Sheltering under an isolated tree
The most well-known and most dangerous mistake during a storm on a hike is sheltering under an isolated tree. It is more likely to be struck by lightning, putting you at risk of a direct strike, an electrical arc, or ground current spreading from the impact point.
Taking shelter in a small cave
A small cave, a rocky overhang or a hollow may seem to offer shelter. In reality, current can travel along the rock face and reach anyone in contact with it. If the cavity is large enough, do not stay near the entrance. Adopt a safety position inside, as far as possible from the ceiling and walls.
Running to escape the storm
The panic triggered by an approaching storm can push hikers to speed up or break into a run. This increases the risk of a fall or a poor decision. Running or taking large strides also raises the risk of electrocution.
Managing the situation after the storm
Once the storm has passed, the combination of dropping temperatures, wind, rain and wet clothing can cause the body to cool dangerously, or even lead to hypothermia. Shivering, clumsiness or fatigue are warning signs that require a swift response.
As soon as the lightning risk subsides, put on your waterproof jackets and windproofs — or even warm layers if temperatures have dropped sharply. If possible, change out of your wet clothing into dry clothes. Wait at least 30 minutes after the last clap of thunder, then resume walking at a moderate pace to generate body heat.
A storm during a hike is one of the most unpredictable hazards in the mountains. With a little planning and the right reflexes, the risk can be significantly reduced. Checking the forecast, postponing a trip or turning back before reaching a summit often keeps danger at bay.
