I can only say 'thank God" summer is halfway (I hope) over. I am really looking forward to October so our temps will be in the 80's and half way livable again. I know Handy down in Tucson feels the same way. We never had a spring this year - we went from cold (for us) to 115 degrees.
Years ago my dad was told he had to get out of cold climate to the warm climate because of his heart problem. Go figure. In the winter while living in Ohio he was told by his doctor to wear a face mask to warm the air a bit.
I think if anything the loss of electrolytes from sweating and not getting replaced is the main reason for dangers of high heat climates. I read that even taking hot showers is worse than taking cold showers because the hot water flushes electrolytes out of the body. Geeze I hate cold showers and I want the water really hot. Maybe not taking showers at all and stinking could be healthy? LOL
When it comes time for me to shower, I turn the water on warm and let the "creeking" in my body loosen up a little and then, I very gradually let the water get cooler. Stepping out of the shower with the A/C on can be a bit challenging because my body temp has dropped so I kind of get a shiver. The human body sweats out a pint of water on a regular day and you don't notice so water consumption is vital. Drink as much as you can. I know I hate getting up in the middle of the night to go pee but it sure beats have cramps and charley horses during the middle of the night. To each his own I guess.