Late June to mid-September is the prime season. The high trails are snow-free, the waterfalls are still running from snowmelt (especially in June and July), and the days are long. July and August are the busiest months — the shuttle bus from Torla runs frequently and the valley fills by mid-morning on weekends. Weekday visits are noticeably quieter.
September is arguably the best month: the summer crowds thin out, the light turns golden, and the beech forest starts to colour. The high routes remain open until the first significant snowfall, usually in October.
Spring (May–June) is beautiful but unpredictable. Snow can linger on the upper paths until June, and some sections may require an ice axe. The valley floor is accessible and the wildflowers are exceptional.
Winter closes most of the high trails but the lower valley is walkable year-round. Private cars are permitted on the valley road in winter (the bus service operates at reduced frequency). Snowshoeing is possible with the right equipment.
The park receives heavy rainfall — the Pyrenees catch Atlantic weather systems year-round. Always carry waterproofs, whatever the season.