Raja Ampat sits close to the equator, so temperatures stay warm year-round. The more useful planning question is not "is it warm enough" but which months bring the calmest seas, clearest water and easiest diving conditions.
The general pattern
Raja Ampat's diving season broadly runs from October through April, when winds are lighter and visibility tends to be at its best across the Dampier Strait and the northern islands around Wayag. The middle of this window, December through March, is generally considered the most reliable stretch for calm crossings between islands.
From June through August, stronger winds from the south-east can make some crossings choppier and reduce visibility in exposed areas, though sheltered dive sites and Misool in the south often remain diveable through this period.
These are general patterns, not guarantees. A specific operator will have a clearer, current view of conditions for your exact dates and route.
Water temperature and visibility
Water temperature in Raja Ampat stays warm throughout the year, typically comfortable in a light wetsuit or none at all for many divers, though a three-millimetre suit is a common choice for repeated dives over several days. Visibility varies more by site and current than by season alone: sheltered lagoon-type sites can stay clear even when open-water crossings are choppier, while current-swept channels such as those in the Dampier Strait can shift from excellent to limited visibility within the same day, depending on tide.
Rainfall and topside conditions
Raja Ampat does not have a sharply defined dry season the way some parts of Indonesia do. Rain is possible in any month, usually arriving as short, heavy tropical showers rather than sustained wet-season downpours. This matters more for topside activities such as the Piaynemo and Wayag viewpoint hikes, which are more pleasant in clearer weather, than for diving itself.
Which months suit which travellers
Divers prioritising calm, current-friendly conditions and the widest range of accessible sites generally do best scheduling within the October to April window, particularly December through March. Travellers with more flexible dates, or who are especially drawn to Misool specifically, have a wider window to work with, since the south tends to be more sheltered from seasonal wind shifts than the north. Travellers whose main goal is manta encounters in the Dampier Strait have comparatively more flexibility, since cleaning-station activity is not as tightly seasonal as general sea conditions.
Choosing dates around a route, not just a season
Because Raja Ampat is large, most liveaboards focus on one or two areas per trip rather than covering the whole region. Dampier Strait, Misool, and Wayag and the Fam Islands each have slightly different conditions, so the best time to visit can depend on which part of Raja Ampat a particular itinerary covers.
If a specific sighting or site is the priority, it is worth asking the operator directly which months they consider most reliable for that route, rather than relying on the general season alone.
Quick answers
Is there a truly bad time to visit Raja Ampat? No month is closed to diving, but June through August brings the most variable conditions in the north, so travellers with limited flexibility often prefer the October to April window.
Do I need to book far in advance for the calmer months? December through March is a popular window, so shared departures during this period can fill earlier than shoulder-season dates.
Is Raja Ampat suitable for snorkelers, not only divers? Yes. Much of the region's shallow reef and lagoon scenery is accessible by snorkeling, and topside viewpoints do not require diving certification at all.