May to October is the main season. Summer brings the most visitors but also the most activities: kayaks, open-air concerts, and the castle's son-et-lumière shows on summer evenings. Spring and early autumn are quieter and arguably more pleasant — the forest walks are better without the July crowds and the light in September is exceptional.
The Ardennes winter is wet and grey, and some restaurants and accommodation close. But winter weekends can be peaceful, the castle is less crowded, and if it snows the valley looks extraordinary.
The Journées Godefroid (Godfrey's Days) festival in August features a medieval market, jousting, and historical re-enactments centred on the castle — a good spectacle and popular with families.