Weather Tour du Mont Blanc (TMB)

TMB Summer Months

The “summer” months are June, July, August and September. Each month is unique, so the type of weather you’ll experience will depend on which month you choose to come.


June is typically quite dry and cool, with valley temperatures at around 18°C (64°F).
In early June, there are often patches of snow on the high mountain passes.


As we move into July, the temperatures increase and we start to see afternoon showers and thunderstorms.
The average valley temperatures are around 21°C (69°F).


August is the warmest month, with valley temperatures sometimes exceeding 30°C (86°F).
Because of these high temperatures, August is often the wettest month.
In August, there is a high risk of afternoon showers and thunderstorms.


By September, the temperatures start to drop again, and we have fewer storms.
You might be surprised by this, but September is actually the driest month!

For more information about the “best time” to do the the Tour du Mont Blanc (TMB), read this post.


TMB trail bad weather
Down from Bovine in bad weather


TMB Weather

Hazard Risks

We don’t normally get showers until the late afternoon. By this time, you can normally expect to be in the safety of your evening accommodation. That said, the mountains can be unpredictable! A beautifully clear day can suddenly change, and with little warning. Because of this, it’s important to be prepared. Make sure you have a good quality waterproof coat, and we recommend using a waterproof bag-cover.

Another factor to consider is the altitude. In one day, it’s not uncommon to climb 1000 metres. The temperatures in the valley are significantly warmer than the temperatures up high. Make sure you have warm layers, and that they’re accessible. Pack them in the top of your bag, so that you can easily put on and extra layer if you get cold. A warm hat is essential, an we recommend that you pack a pair of thick gloves.

Inclement weather such lightning, flash floods, fog and snow may or may not be predictable. They may require immediate response for safety.


Safety in the Mountains (Self-Guided)

The vast majority of TMB trekkers complete the circuit without any problems. We’ve been guiding clients around the TMB for almost ten years, and we haven’t had a single incident. It’s safe to say that accidents on the TMB are rare! That said, there are always objective dangers when out in the mountains, so here are a few “dos” and “don’ts” to help you keep safe in the mountains. These are especially important for self-guided trekkers, but guided clients might also find these useful.

Plan Each Day.

Study the statistics of each day, making note of the distance and elevation.
Don’t over-estimate your fitness, or the fitness of your group.
Make sure to give yourself enough time to get down safely.
Re-evaluate at the end of each day. Plan to set off earlier if need’s be.

Check the weather forecast.

Check the weather forecast as often as possible. When you are in the towns, the easiest option is to use the online forecasts online (scroll down for more information). Alternatively, you the Tourist Information Centres will be able to give you a weather forecast.
When you are up high, you might not have signal or internat. Most mountain refuges display the forecast in the dinning areas. If this is not apparent, you can ask the refuge guardian.
While you’re on the trail, look for signs of weather deterioration.
If you notice that the weather is quickly deteriorating, it’s better to go back or to wait for it to pass than to venture into dangerous, exposed areas.

Avoid lightning…

If a storm is forecasted for the late afternoon, make sure to set off early.
Thunderstorms can normally be avoided with good planning.
However, if you do find yourself on the trail during a thunderstorm, avoid mountain passes (“cols”) and exposed ridges.
Don’t climb out of the forest, and don’t shelter under rocks.
Instead, take your rucksack off and kneel on top of it. This keeps you safely off the ground.
Put your head down, and put your hands on your knees.
If you have been using poles, make sure to drop them; do not hold onto anything that is made out of metal.

Carry a first-aid kit.

Make sure to carry a first-aid kit. The following items are essential : plasters, blister plasters, alcohol wipes, a bandage that can be used for cuts or to strap up a strained ankle. We also recommend that you pack a foil blanket.
If you’re doing a Self-Guided TMB, we’ll provide you with a simple first-aid kit and a foil blanket.
Take a few extra rations of food, and carry more water than you think you might need.
Be vigilant to signs of fatigue or sickness, in yourself and in others. Remember that the altitude can affect some people more than others.
For self-guided trekkers, you could consider having one of your group do a simple First-Aid Training.

Accident protocol. 

In the unlikely event of an accident, make sure the injured person is in a safe place.
Keep the injured person warm by giving them warm layers of clothing, and putting them into a foil blanket.
If you have signal on your phone, call 112. This number can be used in France, Italy and Switzerland.
There are a few areas on the TMB where you might not be able to get phone signal. In these areas, you will always be close to a mountain refuge, so the best thing to do it to send one person (if possible) back to the refuge to seek assistance.
For Guided-Trekkers, your guide will carry an emergency satellite phone.


Autumn colours in the Berard valley.

Online Weather Forecasts

The TMB Classic Route passes through 3 different countries (France, Italy, Switzerland). This can be confusing when trying to find an up-to-date and accurate weather forecast. Here are the online forecasts that we use, and that we find the most accurate :

France: Chamonix – Meteo

Italy: Weather Forecast Autonomous Region Aosta

Switzerland: Meteo Swiss


When is the best time to do the Tour du Mont Blanc (TMB)?

Each “summer” month is uniquely beautiful. The best time to do the TMB is highly subjective, and will depend on your own personal preferences. For example, do you prefer warmer or cooler temperatures? How likely is it that you’ll want to shorten a day? Find out which month would be the best for you by taking this quiz.

Créé par Grant and Joel

When is the Best Time to do the Tour du Mont Blanc (TMB)?

Use this free personality quiz to find out when would be the best time for you to do the TMB.

1 / 7

Which would you prefer, autumn colours or snowy mountains?

2 / 7

Which of these best describes you?

3 / 7

How likely is it that you'll want to shorten some days on the TMB?

4 / 7

Which of these best describes you?

5 / 7

Would you like to try lots of different local dishes?

6 / 7

Which of these best describes you?

7 / 7

How would you feel if you didn't see many alpine flowers?

Share this Quiz!


by Grant and Joel

Grant and Joel are local guides, and they are the co-owners of Happy Tracks. They both live in the Chamonix valley year-round. You can find more information about Grant and Joel on the Our Guides Page.

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