The best months are May, June, September, and early October — warm, dry, and quiet, with the surrounding vineyards in leaf or harvest. July and August are hot (often above 35°C) and busy with the Chorégies festival, when the theatre fills nightly and hotels charge premium rates.
The Chorégies d'Orange opera festival runs from early July to early August — book accommodation and tickets months in advance. The mistral, the cold northern wind, can blow strongly in winter and spring, sometimes for days at a time.