Quick answer: November–April is the dry season with calmer seas. May–October is monsoon season — many day trips still run, but Similan National Park may close.
- Nov–Feb: Best visibility, busiest at Phi Phi and Maya Bay
- Mar–Apr: Hot, still calm; good for Similan and Racha
- May–Oct: Fewer tourists; check weather daily; some routes adjust
Plan your trip: boat tours, fleet, island guides. Private charters: yachts · catamarans.