Program Changes Due to Weather Conditions

In light of the current prefectural alert and the latest weather reports we have received, we convened the Race Committee this morning to adjust the schedule for the 2026 Mont-Blanc Marathon.

Forecasts for the coming days call for alternating periods of extreme heat and the risk of thunderstorms. In light of this, our top priority remains your safety, as well as that of our volunteers, our staff, and everyone involved in the event.

At this time, only the 23km and Mini Cross races are subject to schedule adjustments.

23 km du Mont-Blanc: start at 7:00 a.m.
Mini Cross: start at 8:30 a.m.

For the other races, no changes are planned at this time.

However, the mandatory water requirements have been adjusted depending on your race (details below).

The Race Committee remains on standby and is closely monitoring the situation. If conditions require it, further decisions may be made to ensure the event runs smoothly and safely.

We understand that these adjustments may affect your plans, and we sincerely thank you for your understanding. Every decision is made with a single goal in mind: to allow you to experience the Mont-Blanc Marathon under the safest possible conditions.

Below are the details of the decisions made at this stage:

Decisions confirmed today:

Friday, June 26: 90 km Mont-Blanc

The start of the 90 km race will proceed as scheduled at 4:45 a.m.

However, the weather forecast calls for high temperatures and a risk of thunderstorms throughout the day.

⚠ Due to the expected high temperatures, please note that a minimum of 1.5L of water will be required for the 90 km Mont-Blanc race.

We remind you that natural water sources (fountains, streams, snowfields) are available along the course; we encourage you to hydrate regularly at each of these points.

If conditions deteriorate, the Race Jury will take the necessary measures to ensure everyone’s safety.

➡️ We ask that you strictly adhere to the list of mandatory gear, which may be checked before the start. This gear is essential for your safety given the rapidly changing weather conditions in the mountains.

Saturday, June 27: 23 km of Mont Blanc

Start time moved up by one hour: 7:00 a.m.

To limit participants’ exposure to the forecast extreme heat, start times have been moved up by 1:00.

The new schedule:

7:00 a.m.: Elite Start Area + Start Area 1
7:10 a.m.: Starting Area 2
7:20 a.m.: Starting Zone 3
7:30 a.m.: Starting Area 4
7:40 a.m.: Gate 5
7:50 a.m.: Starting Area 6

⚠ Due to the forecast of extreme heat, please note that a minimum of 1L of water will be required for the 23 km Mont-Blanc race.

Saturday, June 27: Mini Cross

Start time moved up to 8:30 a.m.

To limit children’s exposure to the forecast high temperatures, the start times have been moved to the morning.

The new schedule:

8:30 a.m.: 800 m
8:45 a.m.: 2 km
9:15 a.m.: 3 km

Please make sure your children have a hat and sunscreen, and make sure they’re well-hydrated before the races start.

Events remaining unchanged: Vertical Kilometer, 10 km of Mont Blanc, The Young Race, Duo Étoilé, and 42 km of Mont Blanc

At this time, no changes to the schedule or course are planned for these events.

Depending on how weather conditions develop, the Race Jury will make all necessary decisions to ensure everyone’s safety.

⚠ Due to the forecast of extreme heat, please note that a minimum of 1L of water will be mandatory for The Young Race and the 42 km du Mont-Blanc.

We remind all participants to bring all required gear, which is essential for staying safe in the mountains regardless of conditions.

As you can see, we are monitoring the weather situation very closely, in coordination with the relevant authorities.

Our goal is to ensure you have a fantastic trail running weekend under the best possible conditions and in complete safety. All of our decisions are made with this objective in mind.

Should further adjustments prove necessary, we will inform you as soon as possible through our various official communication channels (email, website, and social media).

Thank you for your understanding and trust.

Weather Report for Thursday, June 25, 2026 – 8 a.m.

The weather forecast for this weekend is essentially the same as it was on Wednesday, June 24, 2026.
We’ll continue to experience a heat wave through Sunday, with a risk of thunderstorms every evening.

Highest temperatures
Chamonix: 32°
2,000 m: 22°
2,500 m: 19°

These temperatures may be lower depending on cloud cover in the afternoons.
We’ll be under a southeasterly flow shifting to the southwest on Saturday, June 27, and Sunday, June 28, 2026.
No wind in the valley; thermal breezes in the mountains will be frequent, depending on the aspect.

It is too early to accurately predict the timing and intensity of thunderstorms over the next few days, though we can expect only light electrical activity.

The next bulletin will be issued tomorrow, Friday, at 9 a.m.