What Mossback said in his two previous posts.
Even though our frost line in the Puget Sound lowlands is only about a foot, I blow mine out since the sprinkler bodies are above that.
I only use about 40-45 PSI, though, since that is close to our actual water pressure. Also, 45 PSI really gets those rotors spinning. I worry about damaging the internals if I go higher. It will also give your compressor a good workout since you'll be moving a lot of air for a long time. I'd make sure to keep it in a cool spot with good ventilation.