I'm in Phoenix and my commute is about 8 miles each way. I've ridden home in temps up to 117, but generally won't take the bike if it's going to be over 115. My usual wardrobe is a regular pair of bike shorts, a technical t, helmet and short finger gloves. Last week when it was 111 I decided to try out a long sleeve technical t, I figured all the outdoor workers you see are wearing long sleeves so why not? Turns out those guys know something about being outside, the ride home with long sleeves was definitely nicer than with short sleeves. I assume the arm cooler sleeves will do about the same so I need to get a pair of those.
Always keep your water bottle full. Not only is it great to quench your thirst, but a squirt of water to into the helmet can help cool you off.
Find the shade when you're stopped at a light. Even the narrow strip of shade from a traffic light post can make a big difference.
Try to time traffic lights, if you can slow down before a light so it's green when you get there it's much better than sitting stopped next to a car with heat pouring off the radiator. I feel that I could ride for hours when it's 110 if I could just keep moving at 10mph+. It's the stops that kill me.