90 degrees is way too hot. he is looking for a place to cool down, and the water dish is the best he can do in your cage. I am in San Diego too, and when it gets over 85, I either take them inside the bedroom with the AC on, or I wrap a gallon size frozen bottle of water with a large towel and put it in the cage/tank. My snakes will crawl into the towel and stay there until the Ice melts....a day or two. If they get too hot, they may die and they certainly won't eat.