The SO and I did a 2-up on July 4th, 500 miles, from NW Phoenix (we're about 25 miles east-N-east of Scottsdale, very top part of NW phoenix)..
Figured it was a good day to try out her brand new air flow suit
It was hot, even in the mountains...went up thru payson, christopher creek, then cut up north on some road all the way to route 40, back west to 87 I thnk it was (sorry, only been here since Jan 07), stopped at natural bridge state park for a couple hour break before heading into the phoenix furnace...i think its at about 8k feet and it was nice there, lower 90's, but most of the mountains were still around 100, payson was showing about 104-106 or so.
August will be tuff if you don't want to hide indoors all afternoon. It is nicer in the mountains (north), maybe up-to flagstaff area its even cooler (sedona)..
but...you might get more enjoyment waiting a bit if you can, as stated already.
oh yeah...the airflow gear worked great, but it was still hot for the pillion, the SO wasn't too excited about riding in that heat again, even though it was nice starting out ealier in the day..rolled into phoenix around 8pm and it was still showing about 108 deg F