Hi Deepika!
August is definitely a hot and humid month to visit Walt Disney World. Here are a few tips for your little one to be comfortable:
Dress him in light clothing. Even just a onesie would be fine for him to wear. Also, a hat with a full brim is great for keeping the sun off his face.
Pick up a good stroller fan. The air inside a stroller can be very stagnant, so the little ones get really hot, especially if they are napping and the hood is down, when there isn't good air flow. There are clip on fans for strollers that are battery powered. Two of them would be better!
Take advantage of the indoor attractions. Alternate between being outside and inside. There are tons of things you can do inside to take a break from the heat, especially shows like
Mickey's PhilharMagic in Disney's Magic Kingdom or
Finding Nemo - The Musical at Disney's Animal Kingdom.
Take a break to cool off in the pool. Head back to your resort in the afternoon for some splash time in the pool. It's a great refresher for everyone.
In my opinion, the best time to visit in August is mid to late August. Schools around the world begin to start for fall in early August, so you'll find the parks slightly less crowded towards the end.
Have a magical day!
Leslie