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Tour du Mont Blanc

Tour du Mont Blanc

Mountain Safety and Weather

Contents List | Introduction | Mountain Safety and Weather | Sample Route Guide

Mountains can be dangerous but not if you are aware of the hazards, are willing to prepare for them and learn how to minimize their potential to happen. Start by wearing the right clothes and follow this up by packing the extra clothing you may need to cope with any deterioration in the weather.

The next step is to learn about the mountains. If you are already an experienced mountain traveller you probably have an almost instinctive awareness of potential dangers.

It is only with experience that you learn how to place your feet to avoid spraining an ankle, which rocks look unstable and what the weather is about to do.


The Tour du Mont Blanc is quite a demanding trek with some significant ascents and descents. it's always a good idea to build up a bit of stamina and fitness before you leave for the Alps and, once there, take the first two or three days steadily.

don't try to do too much each day.

The first few miles of the Tour offer quite a tough introduction with over 600 metres of ascent from Les Houches to Col de Voza. If you find this exhausting, don't let it dishearten you: it does get easier once you have a couple of days’ trekking behind you.

it's worth keeping the first day as short as possible because of the tough ascent to Col de Voza. For this reason, it's wise to stick to the less strenuous main route via Bionnassay unless you have already done some trekking recently, in which case the variante route should prove more rewarding.


Effective pieces of equipment are the ingredients for enjoying the mountains. The essentials are strong boots, clothing that can cope with the worst the weather can serve up, a comfortable rucksack or daypack and a water bottle or pouch.

There is a huge market for outdoor clothing and boots, so much so that manufacturers have gone to great lengths in researching and developing the best materials for walkers’ needs.

Unfortunately a lot of outdoor clothing is expensive but don't be tempted to take shortcuts. While it is not necessary to buy the priciest jacket or boots, it is important to buy the right equipment that will last and will keep you safe in a potentially hostile environment.

The most important consideration when browsing for clothing is to ensure you have all the correct layers: a base layer that wicks moisture away from the body, a mid-layer that traps heat effectively and an outer layer that is waterproof, windproof and breathable (enabling moisture to escape easily).

The big no-no is denim jeans, which trap moisture, stick to the skin and are very slow to dry out. For more detailed advice on clothing and other equipment.

Food and water
Choosing the right type and quantity of food and drinking enough water are both essential for getting the most out of a day. Doing so not only maintains energy levels and keeps morale high but also helps to minimize the risk of exhaustion and other ailments such as hypothermia and fatigue which can lead to clumsiness and accidents.

The body burns up a lot of calories when walking up mountains so these need replenishing. As a rule, men need between 2500 and 3000 calories per day and women 2000 and 2500 calories, depending on how strenuous the walk is.

Eat a good breakfast. Serviced accommodation will usually offer cereals, bread and orange juice. For lunch, some high-energy food such as tuna sandwiches, bananas, nuts, raisins and chocolate will keep you going, and for dinner treat yourself to a good meal with lots of carbohydrates such as pasta or rice.

Restaurants and serviced accommodation in the area offer a range of meals from local specialities such as raclette and fondue to more international flavours including spaghetti bolognese and salmon.

Trekkers lose a lot of water through sweating so drink regularly. On average the body needs around two to four litres during the course of a day. On particularly hot, sunny days this amount may need doubling.

Mountain streams are generally safe to drink from and the majority of trekkers happily do so but it is important to use a little commonsense when choosing a drinking spot. Choose tributaries rather than main rivers and avoid any water source that is downstream from buildings or farmland.

The nearer to the source you are, the less probability there is of something dead lying in the water upstream.

If you are not happy with drinking directly from streams (there is a very small risk of contracting giardia or finding something smelly and organic in the water after having drunk from it) fill your bottle up with tap water at the start of the day or use water purification tablets or a couple of drops of iodine.

Blisters and other foot issues
It isn't the mountains ahead to climb that wear you out; it's the pebble in your shoe.
Muhammad Ali

Blisters occur with excessive friction on vulnerable spots like the heel and the ball of the foot. The chance of a blister developing is even higher with wet feet. Prevention is definitely better than cure when it comes to blisters.

Make sure boots fit well and that there is not too much slippage. Orthotic insoles such as Superfeet are a worthy investment that help stabilize the foot. They also improve overall posture and therefore minimize stress on knees and other joints.

If you feel a blister may be developing, don't ignore it, hoping it will go away. Apply a dressing before it gets nasty and it becomes too painful to walk on. Blister kits such as Second Skin and Moleskin are excellent at protecting tender spots from further abrasion.

If a blister does develop, try to avoid popping or tearing it. If it does burst, apply antiseptic cream to prevent infection and then put on a dressing.

Boots must also be waterproof. Use a boot wax on leather boots. It is also best to ‘break in’ new boots by wearing them round the house before setting off into the mountains.

Hypothermia is the cooling of the core body temperature due to exposure to the elements. It is a potentially lethal condition but is totally avoidable. The wind, cold and rain are all elements that can lead to a case of hypothermia but their potential to cool the body's core (where all the vital organs such as heart, lungs and brain are located) can be minimized by preparing for them.

Make sure the clothing you have insulates well, is breathable, effective in repelling water and windproof. And remember that it is just as important to take layers off to avoid sweating too much (which can lead to cooling of the body) as it is to keep layers on when it is cold.

Other factors that can increase the chances of hypothermia include exhaustion and dehydration. Combat these by eating high-energy food, drinking regularly throughout the day and ensuring you are fit enough for the planned walk. Spending some time training before a trip is very wise.

The early signs of hypothermia to look out for in a companion include occasional shivering and complaining of feeling cold. If nothing is done about this, the condition can worsen.

A person can be considered hypothermic once the shivering becomes uncontrollable. Other obvious signs that may or may not be present in an individual with hypothermia include irrational behaviour, slurring of speech, irritability, clumsiness in walking and refusing to accept that anything is wrong.

If you are alone it is essential to be aware of the early signs and to act accordingly since it becomes much harder to think straight and be rational once the condition progresses.

Anyone can and must treat an individual if they appear to have hypothermia. Find the nearest shelter or use a bivvy bag and make sure there is some insulation from the ground (a rucksack for example).

Replace a patient's wet clothes with dry ones and give him or her food and a hot drink. Stay close to the patient to provide additional shelter and warmth and talk constantly in comforting and encouraging tones.

It may take some time for the patient to recover a sense of normality so it is also important to make sure you and anyone else in the group is warm and dry. When you are sure it is safe to continue, descend immediately by the quickest and safest route.

If it becomes obvious that to continue would be too dangerous you may need to send someone to summon help. The best way of avoiding hypothermia is to not allow it to reach such a stage.

River crossings
Most streams and rivers on the Tour are bridged. There are a few exceptions, notably on the approach to and descent from Col de la Seigne, on the Val Sapin Variante Route at La Trappe and between Plan de l�Au and Alp Bovine.

None of these crossings is difficult and in good weather you won't even get your feet wet but in bad weather they may be impassable so be prepared to change plans.

If you have to cross a deep stream or river the best technique is to face upstream and cross with the aid of a strong stick or trekking pole which increases stability. Do not cross bare-footed since your boots will help grip on slippery rocks.

Move steadily across the river, ensuring that every time you place a foot down you have a firm hold. When there is more than one person, cross in groups of two or three. With two people the partner stands behind the person holding the stick and holds on, moving in time with their partner.

Three people can cross in a huddle with arms around each other's backs.

Dealing with an accident
The Tour du Mont Blanc is a popular trail so finding help in the event of an accident should not be too difficult. If you or a companion has an accident, follow these steps:

- Use basic first aid to deal with any injuries but do not overstep your own knowledge or ability

- Work out your position and make a note of the grid reference on the map

- If you have a mobile phone, call for help (see box opposite)

- If you don't have a mobile phone try to attract attention by blowing a whistle, or flashing a headtorch if it's dark (six blasts or flashes repeated after a minute is the international distress call)

- In a group, leave at least one person with the casualty while others go for help. If there are two of you, you must decide if it is safe to leave the casualty alone. If you do, leave some spare warm clothing and food with the patient and remember to keep a note of the grid reference.


There is no such thing as bad weather, only bad clothing
Norwegian saying

Along with the terrain, the weather is the most important factor affecting a trek in the mountains in terms of enjoyment, aesthetics, comfort, difficulty and, most pertinently, safety.

Understanding the weather is so important and yet it is often overlooked. The weather in the valleys is usually very different from the weather at the top of a col and, more often than not, it is usually worse at the latter.

However, bad weather does not necessarily mean that a day's trek has to be abandoned. While walking in very extreme weather is quite foolish, walking in a bit of rain or a gusty wind can make for a most exhilarating day if you are prepared and clothed for the elements.

To know what weather to expect it is important to know how it works. During the summer, high-pressure systems, or anti-cyclones, usually bring settled weather, often with sunshine but not always.

Low-pressure systems are bad news for the Tour du Mont Blanc trekker as these tend to bring rain, wind and thunderstorms.

Weather fronts, marking the boundary between warm and cold air masses, are usually quite benign when associated with high pressure, often leading to cloud and maybe a little light rain. Conversely, with low pressure, they are active affairs that produce prolonged precipitation.

There are three types of weather front.

Cold fronts, where colder air replaces warmer air, bring intense rainfall that generally lasts for around six to twelve hours.

Warm fronts, where warmer air replaces colder air, usually result in less intense rain but it lasts much longer. After the passage of a cold front the weather often turns showery but the visibility improves dramatically; a good time to enjoy wide-ranging views.

Finally, occluded fronts mark the point where a warm and cold front have merged, often bringing prolonged spells of rain.

Understanding cloud
The weather, especially in the mountains, is extremely complex and difficult to forecast but there are some indicators that help us predict what is likely to happen.

Reading the clouds is the best way of determining the likelihood of a breakdown in the weather. Weather fronts bring about the biggest changes and as they pass over they invariably bring precipitation.

In clear weather look out for high cirrus clouds (sometimes called mares’ tails). These wispy clouds are over 10km high and signal the approach of a frontal system.

In some cases a large area of high pressure may effectively block the weather front or divert it but more often than not expect the weather to deteriorate within the next 12 to 15 hours.

If the sky on the horizon looks milky and grey this is an even surer sign that the weather front is making progress as stratus clouds build up. If the cloud appears to be thicker and begins to lower to cut off the tops of the mountains precipitation is likely at any time.

After the passage of a front there is often a spell of sunshine and showers. However, in the mountains it is very hard to predict where the showers are most likely to occur.

You can usually see them coming but how long they last depends on a number of factors, including wind direction and topography. As a general rule the lee sides of mountains are drier because of the rain shadow effect, in which most of the rain falls on the side of the mountain exposed to the approaching weather.

While winds do, in general, increase with altitude there are other factors to consider such as topography. Wind often gets forced through narrow passes, so a gentle breeze on the approach to a col can turn into a gale when you get there.

Once the wind speed starts gusting at around 40mph, walking becomes quite awkward. Above 50mph the wind can quite easily throw a walker from his or her feet.

Add to this the risk of becoming exhausted by fighting against a strong headwind and the wisest course of action is to descend to a lower altitude.

Everyone knows that it feels colder when the wind blows. This cooling effect caused by the wind is known as windchill. Windchill dramatically affects how cold it feels and can lead to exposure and hypothermia.

For example, in winds of just 10mph a temperature of +5 degrees Celcius will feel more like -2 degrees Celcius and at speeds of 40mph it will feel more like -10 degrees Celcius.

When you look at these figures, the case for a good windproof jacket and warm clothes becomes quite evident.

Rain, snow and ice
Just as the wind gets stronger with altitude and the temperature decreases so levels of precipitation increase. Roughly twice as much rain falls at 2000 metres than at 1000 metres.

This is down to the cooling of moist air as it is forced over high ground, leading to condensation and eventually the formation of raindrops that can no longer be suspended in the air.

Rainfall is only a problem if the clothing you have is not up to the job of repelling it. A wet walker first becomes an unhappy one and then potentially a hypothermic and dead one.

Snowfall occurs as the temperature approaches or drops below freezing point. It is unlikely to be a problem in summer although it can fall at any time of year on the high passes that the Tour du Mont Blanc crosses and is not at all uncommon in spring and autumn.

When the ground temperature reaches freezing point, ice begins to form and any snow falling begins to settle. In such conditions it is wise to head down to a lower altitude and maybe wait a day before continuing your walk.

Snow that is already on the ground from winter snowfall can and does last on high ground well into the summer. Even in late August there will be some sizable patches on north-facing slopes above 2000 metres.

Try to avoid large snow patches if you are not used to walking on them but if they are unavoidable kick some steps into them before putting all your weight upon them.

The upside of so many people walking this trail is that plenty of feet have already stamped down good firm foot holes in these late snow patches, which makes crossing them much easier.

Sun and heat
Always apply high-factor sun cream to exposed skin when walking in the summer. The sun's rays are surprisingly strong in the mountains and many people are not used to the long exposures to them that come with trekking all day.

Sunburn even occurs on cloudy days and if there is snow on the ground 99% of the sun's rays are reflected straight back from the surface directly onto vulnerable areas such as bare arms, legs, lips, ears and shaved chins.

Temperature lapse rate
As a rule of thumb the temperature drops at a rate of 1 degree Celcius for every 100 to 150 metres of altitude. In one day on the Tour du Mont Blanc you may climb 1000 metres or more so while the temperature in the valley might be 25 degrees Celcius don't be surprised if it's a chilly 15 degrees Celcius at the pass.

Summer thunderstorms are common in the Alps and they are violent. Hot weather invariably results in an afternoon or evening storm. This is not a time to be out and about and certainly not a good time to be on any exposed ridges or cols.

Local weather forecasts are usually posted at refuges and will warn of any storms (orage in French). If you don't know the forecast, keep an eye on the sky; the build up of towering anvil-headed cumulonimbus shower clouds are an obvious sign of a thunderstorm developing.

The best way to avoid a lightning strike is to stay indoors. If you do get caught out, keep well away from cols and ridges, which receive most direct strikes. Never shelter beneath trees, in caves or below cliffs, all of which act as channels for electrical currents.

If a thunderstorm is building the only course of action that should be countenanced is to descend at the next safest opportunity.

Walkers who have been struck by lightning and survived report a tingling sensation prior to the strike. Should you start to get that prickling on the nape of your neck get as close to the ground as possible. Sit on your legs and tuck your head under yourself on the ground.


You are strongly advised to get specialist insurance for travelling in the mountains. Mountain rescue is extremely expensive so having a tumble whilst trekking or climbing without insurance could cost you more than just an arm and a leg.

The British Mountaineering Council has an excellent range of insurance options for the adventurous traveller. Other insurance companies may also offer to insure you but be sure that they cover you for rescue from the mountains. Most of them specify the altitude up to which you are covered.

If you are sticking to the Tour du Mont Blanc trail you will go no higher than 3000 metres. If you intend to climb Mont Blanc (4810 metres) you will probably need a more expensive option that covers Alpine mountaineering.

Tour du Mont Blanc