Hey Carrie!
It's lovely to see you here again at planDisney! Florida weather can be unpredictable any time of year in Walt Disney World but don't worry as you can still have a great time even on rainy days! Don't let it intimidate you and with good planning, you may enjoy it just as much as I do.
I have found that in August, it tends to rain every day but in short bursts. My first tip is to make sure that you and your family have everything they need to have a safe and relatively dry time. I like to bring plastic ponchos or a light packable raincoat from home to have ready with me to use in the Parks. I also try to wear shoes that are either waterproof or quick-drying. When I have my stroller, I make sure that I have a rain cover that I fasten on it when I park it in Stroller Parking before entering an attraction. I can't tell you how many times I have come back to find it had rained when I was enjoying a ride. Your little one will not enjoy sitting on a wet seat. I also like to pack extra socks for each family member who may need them and a towel or two just in case we need to dry off. Water, heat, and a lot of walking can cause blisters and rash so I always bring some blister bandages and cortisone cream to help survive the day.
If there is a sudden rain storm, most rides tend to keep functioning perfectly fine in all of the Parks. Seven Dwarfs Mine Train in the rain is an exhilarating experience as it is an outdoor roller coaster. Other rides in
Magic Kingdom Park that have outdoor components are Astro Orbiter, The Barnstormer, Big Thunder Mountain Railroad, Dumbo the Flying Elephant, Jungle Cruise, Liberty Square Riverboat, The Magic Carpets of Aladdin, Tom Sawyer Island, and Tomorrowland Speedway. An outdoor ride that could be affected by weather at
EPCOT is just Test Track but exploring World Showcase may not be as fun in the rain.
Disney's Hollywood Studios has only Slinky Dog Dash as an outdoor ride.
Disney's Animal Kingdom Theme Park has a lot of experiences outside such as their walkthrough animal exhibits, shows, Kilimanjaro Safaris, Kali River Rapids, TriceraTop Spin, and Expedition Everest- Legend of the Forbidden Mountain.
However, there are still a ton of attractions and shows in Walt Disney World that are indoors. There could be a queue that extends outside but the experience itself is indoors or in some covered space such as Peter Pan's Flight or Mickey and Minnie's Runaway Railway. If there is lightning in the area or strong winds there is a chance some of the outdoor rides will be suspended from operation for safety reasons. You will be able to see if a ride is not operating by checking out your My Disney Experience Mobile App which will show Wait Times on the map feature as empty or "Temporarily Closed." You may find that Parades, stage shows, and even nighttime spectaculars could be delayed or canceled as well. If that is to occur, you will hear announcements in the Park letting you know what is going to happen. If you are lucky and the rain conditions are not too bad you may catch the fun and rare Magic Kingdom Rainy Day Cavalcade.
I have found that even with flooding rain conditions, I can still walk around the Parks dodging the largest of puddles and get myself inside a queue or indoor show. I also find the storms a great time to take a forced break and rest with a snack. Walt Disney World is prepared for this and they will make sure that even in the rain there is fun to be had.
I hope this help and if you have any more questions please feel free to come back again! Happy Planning!
-Nimmy