The textbook answer is 101.5 is the normal temperature. Size of the dog has no effect on this. In people, some can have a normal temp of 98 or 97.5 or 99. This is true also in dogs, 100.5 or 102 may be normal for some dogs.
If a dog is stressed, just rode in hot car to see the veterinarian, a temp up to 103, I would contribute to the environment unless there was reason to believe the dog was ill.
A low temp can be more of a concern than a high one. Below about 99, certain bodily functions cannot occur. Enzymes responsible for critical functions- energy metabolism, waste removal, and other necessary reactions at the cellular level cease to be able to carry on. A low temp can mean systems are shutting down.
A very high temp also has its serious concerns. Over 106 or so, some things that can happen are cerebral edema or fluid building up in the brain causing seizures and decreased awareness of surroundings. Another complications that the intestinal lining begins to let go and is sloughed, or passed out with stool. Certain breeds are more commonly affected, greyhounds being one.
I hope this helps
That you very much for your thorough answer. I have always been confused on this issue.
Thank you for your prompt response