I am not in a humid climate.
That said, I have not noticed any excess panting with either of our dogs.
BUT...they are black (and rust) and their coats get hot very quickly. VERY quickly. And that does lead them to get hot and to pant as a result.
So I try to keep them out of the sun and heat when they are exerting themselves.
If you have a funny feeling about it, I would for sure have your vet check the dog out.
It is also the case that there is no way for us to know how much exertion your dog is getting when you believe he is prematurely hot and panting. 7 months is still a puppy, no matter how big he is, and he'll still be a growing dog for many months to come. No forced exercise, including walks that are longer than the dog can manage easily. And we have to judge that; often these dogs have drive such that they simply will NOT quit, no matter how far beyond their actual capacity an activity has become.