I noticed as my dog has aged (he's now 14) that he gets cold quite easily. That said, I never bath him in the winter months because he has a hard time warming up afterwards and shivers for hours. This winter I realized that a good way to guage his body temperature was by feeling the tips of his ears. When he's internally cold, his ear tips are cold. He will start to shiver if I don't warm them (the ears) up. I can also warm him considerably simply by massaging along his spine, up and down. I also give him a good scratch over his entire body since that too warms him up. His ears get nice and toasty by the time I am finished and he has a satisfied glow!