Late spring through early autumn is the time to visit. From May to early October the gorges are open, the canoe rentals are running, and the causses are warm enough for long walks. July and August get genuinely hot — 30°C is normal in the valley — and the popular spots like Sainte-Énimie fill up, so consider June or September if you have the choice.
Spring is good for wildflowers on the causses and for seeing the vultures with chicks on the cliffs of the Jonte. Winter is quiet: the town stays open but most gorge activities and many cave tours close from November to March. The viaduct itself is visible year round and is striking in autumn mist.
The annual Festival des Hivernades brings street music and traditional dancing to Millau in late July, and the Causse de Larzac sheep festival in early October celebrates the cheese trade.