UTMB course

Source: The distance and the ascent are from the race organiser (montblanc.utmb.world). We calculate the descent from the organiser ascent and the elevation difference between the start and the finish. The elevation profile and the gradient data come from a 25 m digital elevation model (EU-DEM). All elevations are to the nearest 10 m (50 ft).

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About the course

Ultra-Trail du Mont-Blanc is a c.108 mi174 km ultramarathon that loops around the Mont Blanc massif, passing through France, Italy and Switzerland. It starts and finishes in Chamonix and runs anticlockwise, broadly following the Tour du Mont Blanc trail.

From Chamonix the route heads south-west through Saint-Gervais and Les Contamines, then crosses into Italy at Courmayeur. From there it continues into Switzerland via Champex-Lac and Trient, then returns to France and finishes back in Chamonix.

The course has roughly 31,800 ft9,700 m of elevation gain and loss and averages around 5,300 ft1,620 m above sea level. Most of it is on trail, with long, sustained climbs and descents between valley floors and high alpine cols.

The UTMB course climbs and descends around 31,800 ft9,700 m over its c.108 mi174 km distance. That's slightly less total climbing than the Hardrock 100 or the Diagonale des Fous. The climbing is more concentrated than on the Lavaredo Ultra Trail, but the course has well under half the total climbing of the neighbouring Tor des Géants.

Ascent & descent analysis

In late August, the valleys around Chamonix, Courmayeur and Champex-Lac are often warm, with daytime temperatures typically around 25°C77°F. On the high alpine cols it is much colder, especially overnight, when temperatures can fall to around 5°C41°F or lower, and sometimes below freezing.

Rain is likely, and late-summer thunderstorms are common in the Mont Blanc massif. They can bring heavy rain, hail and sudden drops in temperature on the exposed high passes.

The weather data has been obtained using the Open-Meteo historical weather API.

Conditions at the start line

The pictograms below show the conditions at the start of the course on the race date in each of the last five years.

Temperature range on course

Temperatures experienced on course are impacted by elevation. The graph below shows the temperature range for the five most recent events at different parts of the course.

Daylight hours

The graph below shows the daylight hours on the day of the 2026 edition (28 August), in local time.

UTMB starts and finishes in Chamonix at roughly 3,400 ft1,040 m and reaches a high point of around 8,250 ft2,520 m at the Grand Col Ferret. The altitude is moderate throughout, adding slightly to breathlessness on the higher cols but rarely a major limiting factor compared with the sheer volume of climbing.