I have seen some thermal images floating around lately, so I thought it would be a good idea to quickly explain how to interpret these images.
Thermal cameras detect infrared radiation and convert it into an image. Radiation increases with temperature, so these cameras can be a nifty tool for looking at temperature. However, they do not measure temperature per se. They measure radiation. For example, the image below is of my short-haired dog Kestrel in a cool environment. At the time, Kestrel had a shaved belly due to her recent sterilization surgery. You can see clearly where her hair was clipped because it is much warmer than the rest of her. This doesn’t mean that it’s the hottest part of her. Other parts are covered in a thin layer of fur, and even that is enough to reduce the amount of body heat she radiates, as it traps some of that heat against her skin where the camera cannot “see”. Her extremities are quite cool, which probably does reflect her skin temperature in comparison to, say, her back, which also has a thin layer of fur. The second picture is of Kivi in the same environment, who has a great deal of fur. His body has a lot of blues and greens, indicating he is radiating less heat than Kestrel is. This is the whole point of dense coats. His cooler coat does not mean he is cooler at this moment. It means his coat is doing a great job of trapping his body heat well away from the air and not a lot of heat is escaping from his body. If the ambient temperature were a lot warmer, would this change his thermal image? I can’t show you an example, but yes, it would, to a degree. For example, if he stood in the sun, it would warm up his coat. Would that mean his skin and body were also warmer? Probably to some degree. We can see that some heat at least can escape his coat, so presumably, it goes both ways.
There is a lot of talk about how bad it is to shave a double-coated dog because they apparently need that coat for insulation. Honestly, we have practically no evidence of how a full coat affects thermoregulation in warm temperatures. Probably to some degree, natural insulation can reduce heating and reduce the intensity of direct heat at least in the short term, but just like any insulation, it has its limits. This scientist doubts that it is by chance that dogs from warm climates and bred for intense bursts of activity are often single-coated. FWIW, Kivi has never been shaved, but we don’t live in the sub-tropics.