The dry season runs from November to June, and this is the best time to visit. The beaches are calm, the sea around the coves is clear, and the Mount Pinatubo hike is accessible. December to February can be cool in the evenings, but days are pleasant.
July through September is typhoon season. The open sea becomes rough, boat trips to the coves are often cancelled, and the Pinatubo trail is sometimes closed by flooding. The heaviest rain typically falls in August and September. If you have flexibility, avoid these months entirely.
October is a transitional month — the seas start to calm but typhoons still pass through occasionally. The turtle nesting season at Botolan starts in October and runs through February, overlapping neatly with the dry season, making November and December the best months if you want to combine beach camping with turtle watching.