What clip should I ask my groomer to give my Shepherd mix for the summer?

I agree with all the answerers. Even though you don't show the dog it will ruin his coat and take away his protection. If you feel he is overheating make sure you have an appropriate spot of shade at all hours to protect him from the sun, also make sure its not closed in so if its windy he can have a breeze. If he enjoys water I would buy a small plastic kiddie pool and fill it, he can climb in if he gets really hot and relax.