Not a local, but I do go every year in May for 10 to 20 days. (and the Fall also). I can only recall two days on vacation that it ever rained all day. But, often there's been rain in the afternoon, usually around 3 or 4, that will last for a hour or two. If it looks like there will be rain in the forecast, I'll usually do the hotel pool in the morning, since it seems that's generally the sunniest part of the day, and try to take the water taxi to the parks before the rain starts, since there's more to do in the parks when it's raining then there is anywhere else on property. USF is better than IOA when it's raining.