Florida here. People here are riding smart by riding early pre-dawn or sunset to night rides. Not many are riding in the middle of the day except those that have to for whatever reason.
Another thing is you northerners have to realize that we're acclimated to the heat because it's over 80 degrees most of the year and upper 80's and above for a good 3 months. You guys have short bursts of really hot temps so you don't get a chance to get acclimated.
Naturally you need to stay hydrated with an electrolyte solution like Gatorade. Water alone may not be enough. A hydration pack is very helpful.
Hose yourself down occasionally with water you keep in a bottle. If you keep your head cool, the rest of the body can pretty much deal.
Ride early or ride late but avoid the hot sun.
Don't push extra mileage or speed right now. Take it easy. You may even want to cut back.