Summer (May to September) is best for families as it typically offers the least rain and serene seas, which makes the beaches safe and ocean swimming and snorkeling possible across the region. Trails are in great condition then too.
Wave riders, however, would do well to come in winter (November to April) when the many beach and reef breaks here are blessed with continuous action.
For the best deals on lodging and for the thinnest crowds on the ground, plan your trip for May, October or November (prior to the Thanksgiving holiday).
August is all about festivals, which are a great way to soak up island culture and connect with locals.