The Caribbean dry season — roughly December to April — is high season on Culebra: sunny days, light trade winds, calm seas, and the island's restaurants and rental fleet operating at full strength. Prices and ferry queues are at their worst. Book ferries and rooms well ahead, especially over the US holidays.
The shoulder months of May, June, and November are an excellent compromise: warm, mostly dry, with fewer visitors. The official hurricane season runs June through November, but the worst risk is concentrated August to October — many small businesses on the island close entirely in September. Culebra was hit hard by Maria in 2017 and the recovery shaped much of the current accommodation and restaurant scene.