Honestly, weather forecasts here are not very accurate.
Since the end of the Hurricane season, trade winds have picked up and the weather has been variable.
The forecast you are mentioning has been very frequent this last month.
Rained-out days are extremely rare, it rains at night very often. In the daytime you can expect a shower or two but nothing that lasts longer that 10 minutes. It also depends where you are on the Island, Marigot for example gets much more rain.
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