The Dominican climate is tropical and fairly stable in temperature year-round — between twenty-five and thirty-one degrees on the coast — so the decision depends more on rain, hurricanes and what you want to see.
Dry season — December to April
The best period and the most expensive. Little rain, moderate humidity, calm seas and reliable sun. It also coincides with whale season in Samaná (January to March) and with carnival (February), which makes it the most complete time to visit.
Christmas, New Year and Easter weeks bring peak occupancy and the highest prices. Dominican Easter is a domestic phenomenon: the entire country moves to the beaches and rivers.
Wet season — May to November
More rain, especially in May and again in August and September. It usually comes as afternoon showers rather than full days, and on the east coast mornings are frequently still sunny. Prices drop noticeably.
Hurricane season runs June to November, with risk concentrated between August and October. The probability of a hurricane directly affecting any specific trip is low, but real: if you travel then, take insurance covering cancellation.
Sargassum
The brown seaweed affects mainly the east and south-east coast — Punta Cana, Bávaro — most intensely between March and August, and varies greatly year to year. The north coast (Puerto Plata, Cabarete) and the Samaná peninsula are much less affected, and the south-west barely at all.
Calendar by interest
For whales: mid-January to late March. For carnival: Sundays in February. For kitesurfing at Cabarete: June to September, when the wind is most consistent. For baseball: October to January. For mountains and Pico Duarte: November to March.
By region
The north coast is somewhat wetter and windier year-round; the east is the driest and sunniest; the south-west is arid and very hot; and the mountains are cool always, with genuinely cold winter nights. Combining two regions in one trip generally works better than staying in one.
National holidays
27 February, Independence Day, coincides with the close of carnival and fills the country. 16 August, Restoration Day, is the other major civic date. Internal travel spikes on both and transport should be booked ahead.