Answer: all year round.
The Islands of Tahiti have the advantage of a tropical climate but with the added benefit of sitting outside the main weather belt of the Pacific.
The islands record some of the highest sunshine hours in the world. Keep in mind that the warm/dry seasons is between April and October with the humid seasons coming in between November through March.
Average ambient temperature year-round in the group is 27oC. Much further away from the equator the archipelagos in the extreme south, the Austral and Gambier Islands, are cool enough to grow coffee and Apples.