In general, dogs should not be clipped in order to keep them cool. Logically and empirically, clipped dogs tend to be warmer in summer. The canine coat is well designed to protect against environmental irritants and dirt, as well as shedding water and maintaining body temperature, and the whole system works so well that I see no reason to mess with it. If it were too hot for my dogs I would alter the environment by moving or cooling or… I tend to spend really hot days swimming in the pond or creek—cool everyone off, exercise everyone, and kill any parasites that are flourishing in the summer heat…
(If all you are interested in is the “answer”, stop reading here… )
However, the apocryphal logic commonly articulated is, in my opinion, erroneous. Many people seem to believe that that the virtue of leaving the coat intact is its insulating value and/or dead air space. This is not true—one does not want to insulate a hot canine body on a hot day. If you doubt this, here are a few examples:
1. Mammals in hot climates have evolved almost universally with far less undercoat.
2. Mammals almost always shed out as much as possible of their undercoat in the warm months.
3. Heat moves from higher area to lower. This process is slowed by insulation. In most circumstances on our planet this means that heat is traveling from the dog outward. Insulation will slow this process.
4. Next time it is really hot, go outside and get in a down sleeping bag. Tell me if you think insulation helps you stay cool. Of course it is not a perfect parallel since our bodies cool somewhat differently from dogs, but it does illustrate the fundamental notion—heat dissipation is retarded by insulation!
5. Go for a walk this summer with a Malamute and a Saluki. Observe.
6. Look at a Bedouin. When they dress for extreme heat, they wear a thin, light-colored outer layer which is loose and light to allow airflow while reducing direct solar heating. They avoid insulation.
If you think about the above, you will quickly see why clipping is contraindicated—it removes the outer shell and leaves only insulation! As time passes the insulating layer grows, and the dog has even more insulation and still no shell! What you want to do is leave a thin outer shell layer to block direct solar heating, but remove as much as possible the insulation provided by the undercoat so that airflow is maximized. Hence the virtue of rakes, coat-kings, blowers, and other tools that help the natural process of removing undercoat while leaving guard coat. If you understand this logic, you can also see that in some cases it might be advised to clip a particular dog—say a Malamute in a warm climate that had tons of undercoat and very little guard coat—this dog might in fact stay cooler without the insulation as long as you kept the clip short all summer. But for almost every dog, maximal cooling will be ensured by leaving the guard hairs and raking out the insulating undercoat!!
The one obvious exception to this general logic is when the ambient temperature in the area around your dog exceeds their body temperature. In this case, one might argue that shaving would improve the rate at which heat can dissipate, and I suspect this is true; however, in all truth, if it is over 102 degrees, I would find more effective solutions—air conditioning, misting, swimming, relocating, etc.