SoCal Mommas I have a question :)

We got stationed here last year when I was pregnant so I dealt with the heat all through that but my concern now that it's getting really hot.. we live on the desert side.. what do you do for babies in this heat? my son is always overheating in his carseat or anytime we go somewhere.. we try to keep the fans going as much as possible and blast the a/c in the car but I'm not sure what else to do to keep his temp down. I don't want him to get dehydrated or heat stroke.