Does it rain much in Orlando in early August?

Yes, August is during the rainy season. It will likely rain daily, usually in the afternoon for 30-60 minutes, then clear up and be really humid. There may occasionally be a completely rainy day, but short afternoon downpours are the norm (and they can pour down HARD). It shouldn't ruin your trip though, there are many indoor attractions you can experience while it rains, plus it can be a good time to grab a bite to eat or shop. You can purchase rain ponchos in the parks; you can purchase them at a local Walmart for a few dollars cheaper.

August is our rainy season. Expect storms in the afternoon. Most days they last about an hour or so, then the sun comes back & it is hot and humid. That is the normal weather pattern July thru Sept/October.

It usually rains in the afternoon. The storms are quick, and things clear up nicely again afterward. It is very humid in the summer, and will be even more humid after the rainstorm.