I have a puppy that will be coming in tomorrow and he will have a hold over for about 3 hrs before he can catch the plane coming to me. How will they make sure he is ok and doesn’t get too hot or cold?

There are people that make sure the animals are okay

Check all the particulars with the airport, the individual shipping your puppy and the airport and get it all coordinated and you'll be fine. Good luck!

There are faculties to keep your dog safe as i witnessed so many dogs there and non appeared not properly taken care of. So al that's important is that you expect the best for before your dog arrives.