January
Not_recommendedDeep winter. See the trail's closed season.
2.7 (Chamonix 1042 m) / -4.3 (Col du Grand St-Bernard 2472 m)°C high · -7.1 (Chamonix) / -9.5 (col level)°C low · 9.1Weather and seasons
Best time to walk the Tour du Mont Blanc
Mid-July to the third week of August is the certain answer: cols clear, every refuge, lift and valley bus running in all three countries, and 14 to 15 hours of daylight. The better answer for a lot of walkers is the first two weeks of September, which give the same clear ground and the fewest wet days of the year at both valley and col level, with beds you can actually book.
What changes through the year
The walking season runs from roughly the last week of June to the third week of September, set by two separate things that do not quite coincide: snow on passes of 2500 m, and when the refuges are staffed. Mid-July to late August is when it all works, and it is also when the huts have been sold out for months, the paths are busy, and the last full week of August belongs to the UTMB race. Late June and the first half of September are the answer for anyone who would rather have space than certainty, late June risking old snow and a half-open infrastructure, early September getting clear ground and the driest weeks of the year but walking into the closing-down. Because the three countries run different refuge, lift and bus seasons, a shoulder-season date needs checking country by country rather than as one season.
Month-by-month guide
February
Not_recommendedThe coldest month at the altitude the route actually crosses. See the trail's closed season.
5.0 (Chamonix 1042 m) / -4.7 (Col du Grand St-Bernard 2472 m)°C high · -6.3 (Chamonix) / -10.0 (col level)°C low · 10.5March
Not_recommendedDaylight is back to nearly 12 hours, which changes nothing while the col-level day still averages below freezing. See the trail's closed season.
8.9 (Chamonix 1042 m) / -2.7 (Col du Grand St-Bernard 2472 m)°C high · -3.0 (Chamonix) / -7.9 (col level)°C low · 11.9April
Not_recommendedThe valleys thaw and the cols do not. Chamonix averages 12.7 C by day; at 2472 m the average day is still below zero and 15 days in the month never get above freezing. See the trail's closed season.
12.7 (Chamonix 1042 m) / -0.2 (Col du Grand St-Bernard 2472 m)°C high · 0.4 (Chamonix) / -5.2 (col level)°C low · 13.6May
Not_recommendedThe month that misleads people. Chamonix is green and warm and the valley walking is genuinely pleasant, while the cols above 2200 m are still winter and almost nothing high is staffed. May also has more wet days at col level than any other month of the year.
17.6 (Chamonix 1042 m) / 4.2 (Col du Grand St-Bernard 2472 m)°C high · 4.8 (Chamonix) / -1.1 (col level)°C low · 15.0Watch for: A warm valley reading tempting people high too early. The Col de la Seigne, the Grand Col Ferret and the Fenêtre d'Arpette are winter mountaineering ground this month, whatever the thermometer says in Chamonix.June
MixedA month of two halves with a sharp split between them, and which half you get is decided by the winter that has just happened rather than by the calendar. Early June the big cols are still under snow and most of the circuit's support is not yet running. By the last week the passes are usually walkable, the refuges have opened and the light is at its annual maximum.
21.2 (Chamonix 1042 m) / 9.1 (Col du Grand St-Bernard 2472 m)°C high · 7.5 (Chamonix) / 2.9 (col level)°C low · 15.8 (the longest of the year)Watch for: Hard old snow on a steep morning slope is the hazard of this month, not cold. Poles help, and on the Col des Fours variant an ice axe may not be optional. Melt-fed stream crossings on the Italian and Swiss sides.July
ExcellentThe month when everything on the circuit works at once. Snow lie on the cols is at its yearly minimum, every refuge, lift and valley bus in all three countries is running, and better than 15 hours of light makes a long stage a choice rather than a race.
23.9 (Chamonix 1042 m) / 11.8 (Col du Grand St-Bernard 2472 m)°C high · 9.1 (Chamonix) / 5.1 (col level)°C low · 15.4Watch for: Afternoon convective storms. The pattern is a clear morning and a sky that builds from mid-afternoon, and a col is the wrong place to be in one, so start early and get the high ground done before the middle of the day when the forecast is unstable. Livestock guardian dogs work with the sheep flocks on the French alpages and on the Arpalle and Alléchère pastures in the Swiss Val Ferret: stop, keep your distance, let the dog scent you and move away calmly.August
GoodUnderfoot and overhead it matches July, and it freezes at col level on only two or three nights in the whole month. What is different is the number of people, and the last full week, which belongs to the UTMB race.
23.1 (Chamonix 1042 m) / 11.8 (Col du Grand St-Bernard 2472 m)°C high · 8.7 (Chamonix) / 5.5 (col level)°C low · 14.2Watch for: The same afternoon storm cycle as July. Heat and water on the long south-facing climbs out of Les Contamines and Courmayeur, which carry little shade and are done at the hottest part of the day by anyone leaving after breakfast.September
GoodTwo different months in one. The first fortnight is, for a lot of walkers, the best of the year: cols still clear, fewer wet days than any other month at both valley and col level, and beds you can actually get. From about the middle of the month the French and Swiss refuges start closing, col-level frost climbs to around nine nights, and it becomes a self-sufficient trip.
19.1 (Chamonix 1042 m) / 7.6 (Col du Grand St-Bernard 2472 m)°C high · 6.0 (Chamonix) / 2.1 (col level)°C low · 12.6Watch for: Daylight is down to 12.6 hours, and the astronomical figure flatters what you actually get: these are deep valleys walled by 3000 m ridges, and the sun leaves the valley floors well before it sets. Bring the long descents in earlier than you would in July.October
PoorThe walking is over before the weather looks it. Valley days still average close to 15 C, but at the altitude the route crosses the average day is under 4 C, there is frost on around 18 nights, it is the second wettest month of the year, and the refuges have gone. A handful of valley places run into the first week.
14.7 (Chamonix 1042 m) / 3.7 (Col du Grand St-Bernard 2472 m)°C high · 2.5 (Chamonix) / -1.2 (col level)°C low · 11.0Watch for: Having no way out of a bad day. The escape lifts have stopped, so a col that turns out to be snowed in means walking back down a valley on 11 hours of light with nothing open ahead.November
Not_recommendedWinter proper at the altitude that matters: the average daytime temperature at 2472 m is below freezing and it is the wettest month of the year up there. See the trail's closed season.
7.4 (Chamonix 1042 m) / -1.3 (Col du Grand St-Bernard 2472 m)°C high · -2.1 (Chamonix) / -5.9 (col level)°C low · 9.5December
Not_recommendedThe shortest days of the year, under nine hours. See the trail's closed season.
2.6 (Chamonix 1042 m) / -3.5 (Col du Grand St-Bernard 2472 m)°C high · -5.7 (Chamonix) / -8.6 (col level)°C low · 8.7 (the shortest of the year)Sources and research notes · 23 sources
- donneespubliques.meteofrance.frValley climate normals for every month: Météo-France fiche climatologique, station CHAMONIX 74056001, altitude 1042 m, statistics 1981-2010. Mean daily max and min, monthly precipitation, days with 1 mm or more of precipitation, and days with minimum below 0 C.Checked 29 Jul 2026
- data.geo.admin.chCol-level climate normals for every month: MeteoSwiss normal-value tables 1991-2020, station Col du Grand St-Bernard, altitude 2472 m, which is within 40 m of the height of the Grand Col Ferret and Col de la Seigne and about 10 km from the route. Mean daily max and min, precipitation, wet days, frost days and ice days used in February, April, June to November.Checked 29 Jul 2026
- api.sunrise-sunset.orgdaylight hours for all twelve months, computed for the 15th of each month at Chamonix (45.92 N, 6.87 E).Checked 29 Jul 2026
- chamoniarde.comclosed season, June ground and services, booking pressure. La Chamoniarde (Chamonix mountain safety and prevention body) gives mid-June to mid-September as the season, says remaining snowfields can make the big passes delicate until early July, and advises booking by spring.Checked 29 Jul 2026
- en.chamonix.comclosed season and June ground: Chamonix tourist office states that winter snow accumulation makes walking at certain altitudes unsafe until the end of June.Checked 29 Jul 2026
- montourdumontblanc.combooking pressure: the official TMB association platform releases the coming summer for all member huts on a single day in mid-October, and only association huts can be booked there. Also the presence of large sheep flocks and guardian dogs, used in July watch for.Checked 29 Jul 2026
- montourdumontblanc.comclosed season: the bivouac and wild camping rules in the Aosta Valley (banned below 2500 m), Valais and the French communes, including the Chamonix ban since 1992 and the booked permit now required in the Aiguilles Rouges reserves.Checked 29 Jul 2026
- montourdumontblanc.comJune and September services: the Les Chapieux and Vallée des Glaciers shuttle from Bourg-Saint-Maurice runs in three periods from mid-June to mid-September, and the Contamines valley shuttle is seasonal.Checked 29 Jul 2026
- refugecroixdubonhomme.ffcam.frclosed season and June services: operator page for a French refuge at 2443 m on the route, giving a June start to the guarded season.Checked 29 Jul 2026
- rifugiobonatti.itMay, June and September services and closed season: this Italian refuge in Val Ferret takes bookings from about 26 May to 30 September, the longest season of any hut checked.Checked 29 Jul 2026
- rifugioelisabetta.comMay, June and September services: operator states an early June to early October summer season at 2195 m in Val Vény, plus weekend opening in May for ski tourers.Checked 29 Jul 2026
- montourdumontblanc.comJune and September services: this Swiss alpage gîte at 2100 m below the Grand Col Ferret shows no availability before July and none after mid-September, a shorter season than its Italian neighbours.Checked 29 Jul 2026
- montourdumontblanc.comSeptember and October services and crowds: this La Fouly auberge runs into the first week of October and then reopens for the winter, and its calendar shows the September loosening in availability.Checked 29 Jul 2026
- montblancnaturalresort.comJune, August, September and October services: Compagnie du Mont-Blanc annual opening table for the Chamonix valley lifts, showing Les Houches opening first in June, La Flégère and Le Tour around the solstice, the Vallorcine side of Balme in early July, and most of them closing between the second and third weeks of September.Checked 29 Jul 2026
- courmayeur-montblanc.comJune, August and September services: the Courmayeur Dolonne gondola, Val Vény cable car and Zerotta chairlift run only from the last week of June to the very end of August, a markedly shorter season than the French lifts.Checked 29 Jul 2026
- courmayeur-montblanc.comDecember and January services and crowds: the Courmayeur ski area runs from late November to mid-April, which is what the valleys are doing while the circuit is shut.Checked 29 Jul 2026
- courmayeurmontblanc.itJune and September services: Courmayeur's Arriva shuttles to Val Ferret and Val Vény are free from about 11 June to late September, and Val Vény is served in summer only.Checked 29 Jul 2026
- montblanc.utmb.worldAugust services and crowds: UTMB Mont-Blanc is held in the last full week of August, with races starting from Chamonix, Courmayeur and Orsières or Martigny-Combe, and road and car park closures during race week.Checked 29 Jul 2026
- saint-bernard.chJune ground and closed season: the Pays du Saint-Bernard tourist office grades the Fenêtre d'Arpette variant (2665 m) as difficult and exposed and warns against it in poor conditions.Checked 29 Jul 2026
- grand-entremont.chJuly watch for: livestock guardian dogs are deployed on the Arpalle and Alléchère alpages in the Swiss Val Ferret, which the route crosses.Checked 29 Jul 2026