Hi, I was in the Dominican Republic in May this year and October last year and both times the weather was great.
In October we had a few downpours early evening but they didn't last long and I came back with the best tan ever. It was really hot and sunny each day. In May it was also very hot and sunny with about one afternoon of rain. I wouldn't worry too much about the weather it was great both months.
I'm returning again on the 3rd of October for 2 weeks, I love the place.
Can't wait less than 2 weeks to go.
sam