One thing I like about Rio, rain or shine the people are out along the beaches. I find late November or early December a crap shoot with respect to the weather. I went Thanksgiving 2011 and it rained five out of the six days.

It does seem at least to me unlike South Florida where it can rain like crazy for a couple of hours and then get sunny Rio when raining, rains all day. I generally find fall to be the dryer period.