Nancy has the right idea, for humans and dogs both. The warmer you keep your house, the cooler it will feel to you both outside. When I get to the desert with a dog, I set the temp on the AC at 85. Yes, we are both hot at first, and I spend a lot of time in not much clothing, but after a couple weeks, you really get acclimated to the heat and it's easier on you both to operate.
I never leave the AC on in a car when the dog is inside. I always leave the rear hatch and windows open. I spend as much time outside doing physical activity as possible in the spring so the dog gets used to the heat gradually if possible. I keep a spray bottle of water on me at all times to mist the dog's belly and paws to aid cooling if they get too hot. I also always have a thermometer with me to keep an eye on their core temp. Anything over 104 and we take a break and cool down.
Hydration is paramount to dealing with the heat, in humans and dogs. I will bait water or sub Q fluids before hard activity in the heat. Hydration is a way of life and not a 1 time event. You don't hydrate the day before a hike. By then, it's too late. You keep the dog hydrated all the time through encouraging drinking and baiting water with appropriate stuff, like homemade beef broth... yum.
Be sure to groom a lot too. Keep those extra hairs from insulating the dog unnecessarily.
My pet dogs get less of this than my working dogs going to the middle east, obviously, but some of it still applies. We keep out thermostat at 80, not 68. They get baited water 3 times a day when we are training in the summer. They also spend a lot of time outside just hanging out. They always have shade and water, but they spend quite a bit of time outside when it starts getting warm, especially Lucian the Cane Corso. He needs all the acclimatization he can get LOL
When a dog saves the life of a man, it becomes clear that partnership knows no bounds.
Fama - T.E.D.D. OEF XI-XII (GSD)(RET)
Marshall - T.E.D.D. OEF XII-XIII (Lab)(SF EDD)
Lucian - Med Alert / Mobility SD (Cane Corso)
Pud - the old man (Pit x Lab)