How long a vacation? Beginning what day? It may mean that you go to Corcovado with the first sunshine that appears, to Sugarloaf if you get another sunny period, and the majority of the time is cloudy. It may mean that it rains briefly once during the day and at night and you get some beach weather otherwise.

(We just came back from Mexico a few weeks ago. The online forecast the week before read torrential rain for all days we were going to be there and I was in a panic, thinking of cancelling. We had sun the whole time; not a drop of rain.)