Raja Ampat has two main seasons for diving. October to April is the drier period, with calmer seas, better visibility, and the best conditions for reaching Wayag and other remote sites. This is the peak season; prices are at their highest and liveaboards are fully booked months in advance.
May to September brings the northwest monsoon, with rougher seas and reduced visibility in some areas. Some sites, particularly in the north around Wayag, become difficult or impossible to reach. However, other sites — particularly in the south around Misool — are often calmer in this period. Manta rays are reliably seen year-round. Some operators offer lower prices in the off-season.
The most important variable is sea conditions rather than rain. Always check with your liveaboard or resort about current conditions for the sites you want to visit.