We were married August 12th of last year. We chose August because we are both teachers and the hotel rates and flights seemed to be more reasonable in August than July. We were scheduled to be married on the beach outside of the wp first thing in the morning. We visited in August 2009 to get a feel for that specific location at that specific time, and it was warm, but not bad at 10:00. In 2010, however, it was especially humid the day before the wedding, so we moved it inside of the wp. We usually visit Florida every August and the weather is generally unpredictable. We are from New England and we find that it is not much hotter in central Florida in August than it is in NE. However, the humidity is fine on some days and umbearable on others. It also rains in heavy (although brief) unpredictable downpours.
Everything about our wedding was great. However, you need to account for the August weather. We did our pictures and our wedding early in the morning. Our reception was at night (at the Living Seas) and we had a breakfast at The Wave in between. This way people would not be forced to be all dressed up walking around in the heat. We also had a beachy wedding (Simple dresses, Tommy Bahama shirts, etc). We had events throughout the week (Group dinner at the Prime Time Cafe followed by Fantasmic dessert party, Breakfast at Ohana after the rehersal, luau the day after the wedding). Since people were casually dressed these days, no one really complained about the heat. It did suddenly start pouring right before the luau, but they have procedures for that.
Basically, one thing we needed to get se in our minds right away is that we needed to be flexible and be resonable, it did mean that we didn't get to do 100% of what we wanted to do, but you do need to consider the confort of your guests. Just keeping these things in mind, you should be fine. We had a fantastic time and people still mention the wedding and how much fun they had.