It does not constantly rain anywhere in the Dominican Republic but a couple hours of rain in the afternoon or evening are not uncomon.
See www.BocaChicaBeach.net/when_to_visit.html for complete weather trends in various parts of the Dominican Republic. Pay particular attention to the variations from year to year, which are so great, that trends haven't been very useful in predicting weather patterns.
It is mostly sunny, year round throughout the Caribbean, usually even on rainy days because rain rarely lasts for more than a half a day.
Weather
