I live in Palm Springs and bike commute. I work at night so my hot commute is on the way to work, so I just ride s l o w. My commute is short (1.5 miles) but it is 110 today. On the rare occasion I go for a long summer ride outside(as opposed to on the trainer) I wet my hair and the inside of my helmet, wear a wet scarf around my neck, freeze my water bottles, drink lots of liquids, pour water on my head and the back of my neck and if I am really over heating I look for sprinklers to stand in or stores with air conditioning. Off the bike I drink about a gallon of water a day and when I ride in this heat I still end up with a headache. I think I need to try electrolyte tabs for outside riding.
I hope some of this helps.
Jones