Les Saintes has two distinct seasons: the dry season (carême) from January to June and the wet season (hivernage) from July to December. The best time to visit is January to April — the weather is warm but not oppressively hot, the sea is calm, and the trade winds keep things comfortable.
December through February is peak tourist season, when charter boats from Guadeloupe and visiting yachts crowd the small bay at Terre-de-Haut. If you want the island to yourself, go in early January before the February–March rush, or in May–June when the weather is still good but the crowds have thinned.
August and September are hurricane season — the risk is real and the weather is unpredictable. October is the rainiest month. If you must go in the wet season, February to mid-April are the driest and most pleasant months within that season.
Les Saintes is small enough that it can feel crowded when several ferries arrive from Guadeloupe simultaneously — weekday mornings are quieter than weekend afternoons.