UTMB Pushes Its Start Back Two Hours and Cuts Its Hardest Section

The UTMB will start two hours late on Friday, at 7:45 p.m. from the Place du Triangle de l’Amitié in Chamonix, after forecasters confirmed a risk of thunderstorms over the Mont Blanc massif for the end of the day. The organization has also taken the Pyramides Calcaires, the most technical section of the 174K loop, out of the course.

The delay carries the rest of the schedule with it. Aid station hours, the assistance points and every cutoff move back by two hours, which leaves the last runners on the course until 6:30 p.m. on Sunday rather than 4:30 p.m. Teams and runners were told late on Friday morning. The new start is 6:45 p.m. in Britain, 1:45 p.m. Eastern and 10:45 a.m. Pacific.

The two hours reduce the storm exposure and cost the race most of its remaining daylight. The sun sets in Chamonix at 8:20 p.m. on Friday and the last light goes at about 8:50 p.m. On the original schedule the leaders would have crossed the first high ground in evening light. Now they will be on that opening climb as the light goes, and most of the field will climb it in the dark. The organization’s statement says the extra two hours should keep runners off the first exposed climbs, the Col de Voza included, until the danger drops.

Additionally, the expected finish time for CCC, the 100K race, has an overlap with the new UTMB start time.

What the Course Change Takes Out

The Pyramides Calcaires sits on the Italian side, above the valley that runs down to the Lac Combal aid station. It is a climb and descent over loose rock that Uphill Athlete’s course guide calls “the most technical part of the course.” Runners will follow the valley to Combal instead.

The bypass is not new. The same section was skipped in 2025, when rain, wind and fog closed in on the Italian side overnight, and again in 2017. iRunFar reported that the 2025 detour removed about 2K and 200 meters of climbing, worth 20 to 30 minutes to the front of the race, enough that Tom Evans’ winning 19:18:58 last year was never weighed against the course record.

“Delaying the start of our flagship race is not a decision we take lightly. But when faced with a confirmed thunderstorm risk, the safety of our runners is non-negotiable. We waited for the latest reliable forecast before making the decision, and we will make the same choice whenever necessary,” Isabelle Viseux-Poletti, the HOKA UTMB Mont-Blanc director, said in the organization’s statement, which also defends the late call: a mountain storm can only be pinned down in the final hours.

What UTMB Has Done Before in Bad Weather

The race has made bigger changes than this one. In 2010 it left at 6:30 p.m. and was stopped at 9:15 p.m. at Notre Dame de la Gorge, with course markers missing between the Col du Bonhomme and Chapieux, as chamonix.net reported. A replacement race was run from Courmayeur the next day. In 2012 the start went back to 7 p.m. and the route was redrawn to stay inside France, about 100K with 6,000 meters of climbing, after snow, cold and wind above 2,000 meters ruled out the Grand Col Ferret, according to iRunFar. In 2014 the main race was cut from 168K to 100K, according to See Chamonix.

The Rest of Race Week

The delay is not the only change of UTMB race week. The organizer’s race pages show the basic kit alert switched on for the UTMB, with a third layer advised for a cold, wet first night. The CCC, which left Courmayeur at 9 a.m. on Friday, is running a course modified in two places in Switzerland, and Thursday’s OCC used a new section between Argentière and Chamonix.

The field that leaves at 7:45 p.m. is missing four of the runners it was built around. Kilian Jornet and Jim Walmsley are out injured, Evans is not defending his title, and Ruth Croft withdrew two days before the start. Jeff Browning suffered a heart attack on the TDS course on Monday, according to his family.

Video and tracking sit on live.utmb.world, and iRunFar is filing written updates from the course. The 46 hours and 45 minutes the runners are given now expire at 6:30 p.m. on Sunday.