The dry season runs November to April and is the best window: warm days, low humidity, very little rain, and reliable diving conditions. December through February are the peak booking months and prices on the all-inclusive packages climb accordingly.
May to October is the wet and hurricane season. June through October can bring serious storms; some hotels close for renovations during these months. The water and the air stay warm, but afternoons often come with heavy rain.
For sea turtle nesting, late May through October is the best time on the beaches at night — though access to nesting sites is restricted and you should not approach without a guide.