Yes you should get a light weight coat if your dog is going to spend time outside...otherwise he'll get sunburned. If its very hot, he also shouldn't be out for long because fur help insulate animals from heat. Some people think they're doing the dog a favor by clipping off the fur when its hot. Not talking about your dog since his fur is causing a problem. Is the fur matted - you may have to be careful with the electric trimmer - the reason - matted fur gets completely matted at the skin and it may hurt the dog.