Short showers as opposed to sustained rain. Good Tradewinds + low humidity and it's dry before you notice.

I played in a cricket tournament in Barbados in July one year and it rained most days but we still got plenty of sun. The showers were short and sharp, usually later in the day. I think you'll still get to enjoy the island for its famous lures -- sun and sand, chiefly -- plus get some good deals on cheaper accommodation.