There are two types of rain patterns in Florida. There is rain associated with weather fronts, which can last an hour, a day, or a week, depending on how long it takes the front to get out of the area. Tropical ones can settle in and really cause torrential rain over several days. Then there is the second type - our typical sea breeze storms that pass through pretty quickly, and normally occur only in the summer and early fall.
In mid March, you should only see rain from weather fronts, so it will be less frequent but may be of longer duration. In July, you should see some kind of brief rain daily, with the possibility of a front or tropical system passing through with a longer rain event. You will have more dry days in March on average than in July, and the humidity and temps will be lower.