Generally the coastal areas will get a short tropical shower almost daily in the evening or at night. And the 'rainy season' varies a little, depending on which coast you are on. On the North Coast, we have a little more rain from October to around January and on the South Coast, there is a little more rain from around May to October.
When it rains, it is usually a brief tropical shower - usually not much more than half and hour. Sometimes we get short sun-showers with a little rain coming down, while still in bright sunlight. At times, there could be a raincloud over one town or city, while the next one is dry.
This is for the Dominican Republic, and not for the Caribbean. :classic: