Depends on location. I live in the Punta Cana area on and off for about 5 years, and have seen it rain at anytime of the year. It's like this everywhere there is a coast. I also have a house near the beach in Florida, and it will rain in my location, but a few streets down it is bone dry
Summer in PC is Rainy Season??
that's a good joke.
summers are the bone dry time of the year.
we get most rain out of the year to fill the ponds during Fall and Winter.
April and May do traditionally add to it, then it only springles once in a while, real lasting rainfalls during summer are seldom(exception is of course in case a summer storm effects the southern part of the eastshores, but those tropical storms and hurricanes are a seldom influence here in the PC area).
and this year, 2015, with actually only 30-35 days of water left behind the Dam-Walls, we are looking forward to a extreme harsh drought for the remainder of this year deep into Fall 2015. ponds all around are already dry, and we just finished May(which did not produce any rain worth to mention it as rain). the country could at this point need a consecutive week of permanent strong rain to fill up aquaeducts slightly above the critical levels, almost a month of rain would be necessary to come to safe waterlevels. ride thru the Hills of Higuey and take a look on those Farmlands/Ranches/Fincas, it is all bonedry, animals suffer due missing water and not much "green" stuff to eat to be found. I fear in a few weeks time we will be at the point when first parts of the Island have human lifes in danger due not available water.
over all, the region has no real "Rainy Season", but during a usual yearly cycle the Dams, Aquaeducts, Ponds get their refill from Fall til into Springtime, and then their levels constantly fall dend Spring til end Summer, which is the clearly dryer time frame of the year.
of course you can catch a good downpoor at any time out of the year, but such happens well more often during Fall/Winter and is a more rare occurance during summer, unless a Tropical Storm comes very close but even those Storms do not make a huge difference to the waterlevels on the Soth of the Eastcoast around PC, they "may" bring some hours of rain, flood poorly drained roads, but 24hrs later all is back to the prior dry level. and even those short storm visits are anyways seldom and do not happen every summer.