The best time to visit Puerto Galera is from November to May, during the dry season. Waters are calmer, visibility for diving is at its best (often 20 metres or more), and the risk of typhoons is low. December to February is peak season — cooler, drier, and very popular with Manila weekenders.
The southwest monsoon (June to October) brings rougher seas and reduced diving visibility, though the dive sites are not closed. July and August see the most rain. The sea crossing from Batangas can be uncomfortable or occasionally cancelled during heavy weather, so check conditions before travelling.