As a dog walker I always checked the temps and watched for any signs that the dog was uncomfortable. DON'T risk walking your dog on the sidewalk or asphalt. Use the grass even if you think your neighbors will mind it will save your pup from burnt paws. I also keep walks and play short in the heat outside. A kiddie pool is a good idea but the best idea is to spend less time outside during the highest heat temps. I know you're thinking what do I do instead. Short training sessions, play fetch inside with toys or a ball, use a puzzle toy for meals and/or plan a short walk in the morning or late evening after the sun goes down a bit.