What To Do in a Thunderstorm in the Mountains » Safety Tips
Whether you're enjoying stunning vistas while hiking or climbing in alpine surroundings – mountain thunderstorms are no joke. Watching the sky turn dark and nature unleash its power can be incredible to witness. But it's also potentially life threatening, and you need to know how to handle yourself when things get dangerous. This guide breaks down how to prep for storms, what to do when they roll in, and what gear will keep you safe when lightning and thunder hit.
Planning and Prep to Keep You Safe
First and foremost, you want to avoid getting caught in mountain storms at all costs. How well you prepare is key for how safe you’ll be when you’re on the move. Always check the current weather forecast and watch for thunderstorm warnings. Especially in summer, storms often build in the afternoon – and they can roll in fast. Start early so you reach your destination with time to spare.
Plan your route with potential shelter spots in mind, like huts, alpine shelters, or bailout routes. During your hike, keep scanning the sky: towering cumulus clouds, anvil clouds (tall thunderheads with flat, spreading tops that signal incoming storms), wind picking up, sudden temperature drops, or electrical crackling in the air are clear warning signs. When you notice these, it's time to find shelter immediately. Even better is avoiding storms altogether by turning around early if you notice early signs of changing weather.
Recognizing Dangers and Acting Accordingly
Mountain weather can flip in minutes – blazing sunshine may suddenly turn into an ominous rumbling on the horizon. When you can spot the warning signs of an approaching storm early and know how to respond, you can effectively protect yourself and others from unnecessary risks. With the right knowledge and staying alert, you can avoid dangerous situations and dramatically improve your safety in the mountains.
Storm Types You Need to Identify
In the mountains, there are mainly two types of thunderstorms that are especially relevant for hikers – frontal storms and heat storms. They differ not just in how they form, but also in their warning signs, how they develop, and the dangers they bring:
Frontal storms usually announce themselves with dramatic weather deterioration, often with steadily increasing winds, sudden temperature drops, and a dark, solid wall of clouds on the horizon. They form with cold fronts and move across the landscape in clearly visible lines. This is actually good news for hikers: Frontal storms are usually predictable, so with proper trip planning you can react in time and find shelter. The danger with frontal storms is their intensity – they often bring powerful wind gusts, heavy downpours, and widespread lightning strikes. If you notice signs like rapidly approaching cloud bands or sudden temperature drops, get out of exposed areas and find shelter immediately.
Heat storms build on hot, muggy days and often develop surprisingly fast – typically in the afternoon after a stretch of nice weather. First signs are towering cumulus clouds that build into massive thunderheads. Heat storms are localized and hard to predict, making them especially treacherous for mountaineers. They can hit even when the sky previously looked clear. That's why it's crucial to keep scanning the sky during good weather periods and react early to the first indications of an approaching thunderstorm – like dark cumulus clouds, rising wind, or distant thunder.
What to Do During a Thunderstorm in the Mountains
When a storm approaches, immediately evacuate exposed areas like ridges, summits – especially summit crosses –, or knife-edge terrain. Water sources, metal structures (like cables on via ferratas), and open areas are also dangerous. If there's no way to turn back in time or reach safety in a hut or similar shelter, a depression, gully, or dense broadleaf forest (preferably deep inside) will offer some level of protection.
In the forest, stay away from old, rotting, or isolated trees, and – if possible – choose a group of young, bendy broadleaf trees instead. In open terrain, get into the lightning position: squat down with your feet together on insulating material like your backpack or a sleeping pad. Keep your feet close together to minimize the risk from step voltage. Put metallic gear like trekking poles, ice axes, carabiners, or wet ropes several meters away. Keep at least one meter, ideally three meters, between you and other people to reduce risk if lightning strikes. This reduces the danger from step voltage that can occur during a lightning strike.
Emergency Shelter at Altitude: When Descents Gets Risky [H2]
Sometimes an unplanned night in the mountains can't be avoided, like when the weather suddenly turns nasty. In this case, a lightning rod-equipped shelter is your best bet. If there's no hut nearby, larger caves offer some protection – keep at least six feet from walls and ceiling to avoid indirect lightning strikes. Caves or overhangs are only truly helpful if they provide at least one body length of depth and at least half a body length of clearance above and in front. Skip wet, small, or low caves – they don't provide safe protection and can create additional hazards.
If none of these options are available, a tall rock wall can provide protection from direct lightning strikes – but only with the proper distance: squat down about ten feet from the wall, making sure you're not sitting directly against the rock face to minimize step voltage risk. Also watch out for rockfall danger. After the last strike of thunder, wait at least 30 minutes before leaving your shelter spot, since straggler lightning strikes can occur.
Staying Dry and Warm: Essential Storm Gear
While proper clothing won't stop lightning, it's still essential during rain and changing mountain weather. Go with waterproof, breathable rain jackets and rain pants that keep you dry while still allowing ventilation. Gaiters protect the gap between boot and pants, waterproof hiking boots prevent wet feet, and gloves protect your hands from getting chilled. Layering lets you adapt flexibly to temperature changes.
Reflective details on your jacket or pack increase your visibility in bad weather or low light. While you should put down metallic items like trekking poles or ice axes during storms, small metal parts on clothing like zippers are no problem as long as you're not in exposed areas.
Ready When the Weather Turns
A mountain thunderstorm is first and foremost something you should avoid, since it's a potential hazard that you should only face – if it can’t be avoided altogether – with knowledge, awareness, and proper gear. When you're prepared accordingly, recognize the warning signs, and follow the key safety rules, you can safely whither the mountain experience, even when conditions get tricky. In our Mammut Stories & Guides you'll also find useful tips on how much weight to carry when backpacking , what a good hiking packing list looks like, and much more.