We just did it this past August! It was an extra trip to see how bad it really is. No DH on that trip. I knew going in it would be hot and rain so I was prepared.
I told people, hey I'd rather be hot at WDW then hot here!
It was HOT and humid. It did rain almost everyday except maybe 2 but it was in the evening around 4:00 - 5:00p so it didn't hurt or schedule much. We brought rags to wet us and refresh us from the resort. We brought bottled water that we froze in the fridge. Lots of sunscreen. Took A/C breaks in shops and had a mid-day sit down meal (tip I got here) to rest and get away from the sun. Start your days first thing early and then leave the park as it starts to get more crowded and hot or take a break eating/shopping or swimming and then head back to a park as it cools down. This worked well for us.
It wasn't as crowded as I thought it would be. The end of August many schools are back in session, like most of Florida. I was pleasantly surprised.
Good luck!