Yeah, we have a definite disadvantage down here in the hot and humid south. When temps are in the mid to upper 90's and the dew point is in the 60's and 70's, evaporative cooling does not work!
You just drip with sweat and look for the nearest place that has air conditioning.
There are days I just do not ride when it gets real hot.
Good for you, failing on the safe side of heat exhaustion or heat stroke is better than tempting it. And that evaporative cooling only works at speed. Some stop and go traffic will set you back and now you will be overheating again.
That iron butt article does a great job of illustrating heat transfer. Heat Transfer and Fluid Flow are not the most exciting topics but it helps to have an understanding for several aspects in life. I may have skipped over it, but it is helpful to know that everyones ability to dissipate heat is different. Several factors change from one to the next including age, weight, health (heart ), probably others. As we get older our "thermostat" may not work as good as it did when we were younger. You also need to be able to get the hot blood near the surface/skin for the heat to be removed. Drug and alcohol can change that too. Some have better blood flow near the skin and can cool better.
I only remember riding once at >95f and I soaked a thermal underwear shirt (thick and holds a lot of water) in water, covered with riding jacket, closed all vents and was laughing at how cold I was getting. It took almost 3 hours to dry out and start getting hot again.