You might wish to spend some time reading on a forum called Traveltalkonline dot com as it has a section full of info specifically related to the BVI.
For weather, you can expect daytime temps to be in the mid to upper 80's, night lows in the mid 70's. A rain shower everyday which may last between 5 minutes and a few hours. Light to moderate winds and seas. All of those descriptions are generalities which may be completely wrong if some weather system rolls through. Not sure where you live, but most professional meteoroligists forecast accuracy is pretty poor more than a few days out. With that in mind, I am not a weatherman, it is pretty hard to predict the weather a month out.
Enjoy your trip if you decide to come down. The time frame you are looking at is just before the official hurricane season starts and you will have a lot choices for anchorages as the peak season will have passed.
many thanks to you who have replied...while the historical weather conditions are to be found recorded on the web, it's nice to to have some qualitative info from those that have been doing this before. hoping to be there late May, early June. Now to find flights and a boat.