Chamonix / Tour du Mont Blanc

On 20 July 2026 the Courmayeur guides collectively stopped taking clients up Mont Blanc's Italian normal route. Two days earlier, rockfall killed a guide and his client in the Grand Couloir — at 02:30, the 'correct' hour. Heat closures now recur roughly every hot summer, and have since at least 2015. Here is the full record, the permafrost mechanism behind it, and why June and September are becoming the smart windows.

The TMB season runs late June through mid-September. July is warmest and most crowded. UTMB race week (August 24-30, 2026) turns Chamonix into a restricted-access zone — avoid it unless you want the festival. Afternoon thunderstorms build from 13:00, peak 15:00-17:00. Start early, be below cols by midday.