Mountain hazards

Mountain hazards


Storms are commonplace in the mountains, especially on hot summer days. Some kinds of storms can develop very rapidly even when the skies are clear.

When this kind of phenomenon is approaching, move away from peaks, ridges and waterways, do not take shelter near runoff channels or chimneys and distance yourself from solitary trees and standing structures (pylons, poles, unusually tall solitary masses...).  Move downhill and seek out dry cover.

If you are in a group when a storm takes you by surprise, leave about 10 meters between each individual (not hand in hand) as you search for shelter. Insulate yourself from the ground using your backpack, rope or any other poor conductor and get rid of any metal objects; do not light fires (which can attract electrical discharges) and wait out the storm: the average duration is about an hour.

To reduce the risk of being struck by lightning, the following should be added to the above precautions:

  • if you have not already done so from home, check the conditions and weather forecast for your route at the guide offices;
  • if you notice vertically developed clouds in the morning, then storms are likely to develop during the course of the day, and are even more likely if there is haziness and a sensation of stuffiness in the valleys;
  • for storms that are already under way, the highest part of the cumulonimbus cloud (typical anvil-shaped cloud) will point out the direction in which the storm is headed;
  • at nighttime, lighting flashes will be visible tens of kilometers away, but if you can hear the thunder then the storm is only a few kilometers away; a delay of about 10 seconds between the flash and the thunder means that your are about 3 kilometers away from the storm (no. of seconds x 340 m);
  • remember - the average storm lasts about 1 hour, and the most intense phase rarely lasts longer than a half hour, so look for shelter (inside caves, not at the entrance) at the first signs of a storm and wait there until it begins to wane;
  • stay away from rivers, which can rise rapidly and present a threat;
  • direct lightning strikes are hazardous, but so are the so-called "ground strikes": the current from the lightning passes through the ground, decreasing in intensity as a function of distance from the strike point - as a consequence, it is important to be touching the ground surface at one point only, e.g., by standing on one foot or crouching with your feet together (there can be a dangerous difference of potential between the sole of one foot and the other; avoid lying down or leaning against the rock;
  • even minor lightning strikes can generate enough current to trigger respiratory or cardiac arrest, burns and involuntary muscle contractions that can induce jerky, uncontrolled movements and even bone fractures. Powerful lightning strikes usually result in death.

After being struck by lightning, however, the victim is not electrically charged and it is safe to administer first aid. The survival rate for lightning strikes is about 80%: save a life with mouth-to-mouth respiration and cardiac massage (CPR)!


Atmospheric temperature is highly variable in a mountain environment: changes in altitude, the arrival of cloud cover and passing from sunny to shady areas are some of the main causes of sudden temperature drops.

There are a variety of factors that cause the human body to get cold, wind is the an exemple.

Wind: an atmospheric agent that is often underestimated and that, as a consequence, can be the source of general discomfort or even outright pathologies. The human body is a machine that produces heat. The main purpose of clothing is not to produce heat, but to hold bodyheat in by insulating the body surface from the outside. The heat exchange between body and air is ongoing, as a matter of fact. In essence, we lose a modest part of our heat through conduction. When it is windy, however, the thin layer of heated air around our body is dispersed more rapidly, which speeds up the exchange of heat. This is why the sensation of coldness can increase significantly even when the air temperature remains unchanged (the "windchill" effect)

Snow and snowfields

Trails can be covered with a considerable amount of snow even early in the season. Beware of slipping hazards - if possible, bypass snowfields if they have even a minor slope and bring the proper equipment: crampons, ice-axe, telescoping poles, snow leggings.

Another snow-related risk concerns difficulties getting oriented: heavy snowcover can hide trail markings and make it difficult to find reference points and landmarks, especially during bad weather. Use a compass and a map or even a GPS.

Caution - following the tracks of other hikers can lead you even farther off the trail!

Keep in mind that waterways can be covered by snow bridges that may collapse under the weight of one or more excursionists, so be careful whenever hiking near rivers, streams and gulleys where water could meet up with snowfields. When a snow bridge has to be crossed, a safety line is recommended. 


Sloping of the ground can create a variety of different complications during the course of an excursion.

Grassy slopes, especially when humid, wet or covered with frost, are very slippery.

The risk of rockslides should never be underestimated, especially when other groups of excursionists are in the vicinity. Proceed with utmost caution when hiking above other groups, and always be aware of your position relative to the possible trajectories of falling rock when downhill from other groups.

While they may seem to offer convenient shelter from bad weather, large masses resting on an incline should never be trusted too much because of their precarious stability.

Never underestimate the potential problems inherent to peaks: open-air ridges, the traversal of very steep slopes and exposed segments can provoke fear and panic. Try to keep your group together and do not leave the trail, however overwhelming it might seem.

Do not try to take shortcuts, and if you ever lose the trail, the best strategy is to backtrack until you find a reliable point of reference.

Fog and limited visibility

Low clouds and fog are very common in mountainous environments. A compass, a map and an altimeter (and being sure you know how to use them) as well as a rescue whistle are handy in dangerous situations and can keep you from wasting significant amounts of time.

In the presence of fog, proceed as a group and follow the trail signs meticulously (even if you already know the way). When visibility is down to a minimum, stop and wait for better conditions instead of venturing out with risky explorations.

Solar radiation

We tend to underestimate just how harmful the sun's rays can be, especially ultraviolet radiation.  They can alter the DNA of our skin cells and induce skin tumors (e.g., melanoma) and other dermatological diseases as well as problems related to the eyes, such as conjunctivitis, snow blindness, corneal burns, heavy tearing and photosensitivity.

The highest risk time time slot is during midday (from 11 am to 2 pm) around the summer solstice (June 21st).  At this time at our latitudes, the sun's rays strike the earth at an angle of nearly 90°, which means the distance they travel through the atmosphere is at its shortest and has less of a filtering effect. In addition, the intensity of radiation increases by 7% for every 1000 meters in altitude, thanks to the increasing thinness of the air. In the mountains, therefore, conditions can vary considerably through the course of a single day.

Another factor to keep in mind is how snow and ice on the ground can increase the intensity of radiation by as much as 100%, thanks to their reflective capacity.

What to do:

  • Wear UV filter sunglasses;
  • Always use high protection sunblock;
  • Avoid prolonged direct exposure of the skin to the sun (do not take naps in the sun or lay out to work on your tan);
  • Take care of particularly exposed body zones (face, ears, neck, scalp, hands).


The equipment of the hiker and all the accessories needed in the mountains


Guidebook: indispensable tool for trekkers on the Tour du Mont-Blanc

Available in different formats and languages, the guide is a critical source of support for organizing your own Tour du Mont-Blanc or personal excursion guide. Accompanied by topographical maps and descriptions of places, paths and shelters, this type of tool explains everything you need to know in case of an emergency, provides background information about the environment, culture and costumes of the Mont Blanc region.

A few examples:

  • Il giro del Monte Bianco, 12 tappe e 48 varianti intorno al gigante delle Alpi, Stefano Ardito, Le Guide di ALP series, 136 pages Cda & Vivalda Editori, 2000;
  • The Tour of Mont-Blanc, Complete two way trekking guide, Cicerone Mountain Walking, Kev Reynolds;
  • Tour du Mont-Blanc - France, Italie, Suisse : panoramas grandioses pour 10 jours sportifs, FFRandonnée;
  • Le valli del Monte Bianco e il Tour du Mont-Blanc, L'Escursionista Editore Guide dell'Escursionista / 1, Luca Zavatta e Carlo Coronati anno 2000.

There are many different topographical maps of the Mont Blanc area, but very few of them cover the entire Tour du Mont-Blanc.
The recommended map scale is 1:50,000, but a 1:25,000 scale map can also be suitable.
For example:

  • ICG Torino: Massiccio del Monte Bianco - Carta dei sentieri e dei rifugi n. 4 - Scale 1:50.000;
  • The Great Treks of the Alps - Scale: 1:25.000;
  • Edition Libris: Massif et Tour du Mont-Blanc - Scala: 1:50.000


The GPS (Global Positioning System) device is a very precise instrument that determines the position of an object by using satellites. The most popular GPS devices also let you load and view your route, so that the user can check their exact location in relation to their planned route as well as the altitude.

Backpack : the hicker's best friend

A large backpack with ergonomic shoulder straps, a comfortable back support with breathable fabric, a waist-level closure and perhaps an extra raincover is an essential element of an enjoyable excursion. A volume of 30 to 60 liters is recommended, depending on whether trekking is planned for one or more days (even if larger backpacks are available). We recommend a model that subdivides the storage space into upper and lower compartments, because two separate compartments can be handy in case of rain or to keep food separate from clothing. Other useful features include external side pockets (no more than two), an ice-axe/poles carrying system, a drinking water setup (e.g., Camelback) and a side zipper that gives you access to the main body of the backpack without necessarily having to remove it from your shoulders.

Footwear: comfortable and longlasting

Hiking boots are probably the most important piece of excursionist equipment. The right footwear lets you to taste the full pleasure of the outing, whereas the wrong boot can ruin what could otherwise have been a wonderful experience. Start out with the models specifically designed for trekking, with a well-articulated sole, shock-absorbing intersole that is still rigid enough to keep you from experiencing the full harshness of the terrain. The upper shoe should be strong and reinforced in the heavy-use zones (especially the toe, but also the heel), allowing a natural bending motion and hugging the foot without squeezing it. An internal hydrorepellant and breathable membrane (e.g., GoreTex®, DryTex®, WindTex®...) can be especially helpful for keeping the foot dry and minimizing blistering and redness. Footwear that is high enough to cover the ankle is recommended for better support and protection from possible sprains; lower shoes can still be used, though they are ill-advised in the presence of snow.

Clothing : How to dress for the TMB

The clothing you choose is critical for excursionist comfort and well-being. There are many different manufacturers of jackets and coats for excursionism and outdoor activities that guarantee breathability, lightness and warmth, and dressing in layers can ensure comfort and convenience.

  • Winter hat: for the cold
  • Summer hat: for protection from the sun
  • Sunglasses: to prevent redness and inflammation
  • Gloves: for the cold
  • Poncho: to protect both body and backpack from rain (caution: not breathable)
  • Scarf: for the cold and wind

Emergency kit

While organizing your trip, be sure to equip yourself with the proper emergency supplies:

  • First aid kit: disinfectant, bandages, scissors, sterile tarp, absorbant cotton, bandaids (classic and for blisters), disinfectant wipes, absorbant gauze bandages, protective gloves
  • Thermal tarp: insulated cover (usually made of aluminum) for protecting the injured and as a cover, if needed
  • Medicine: several pain-relief, fever-reducing and anti-inflammatory pills, ointment for scrapes, anti-histamines (for allergies), mineral salts, diarrhea medicine, insect bite cream, ointment for treating burns
  • Whistle: essential tool for attracting the attention of rescuers and finding each other when separated


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