Best thing would be to move him to the room with AC for the summer. Prolonged temps above 82-83 cause stress and lead to death. If you have a temporary situation where it is too hot you can mist with cool water and run a fan to help cool down the enclosure (but you have to do this repeatedly and closely monitor temps with a temp gun). I had to do that once when my AC went out in the summer. But I could tell the geckos were getting stressed at the 82-83 mark and pretty much had to spend a couple hours in the room misting and running multiple fans into cages until a backup window unit AC could be put in.