Trouble really is not so much the heat as the high humidity that comes with it over here, after a while the fans become ineffective really as the air is already laden with moisture so the fans cease to dry your sweat up. With A/C, it just seems to wick away much more moisture, but like BD said it is so expensive over here to install it for just maybe 2 weeks a year when it would be used.
I have thought about sitting and also sleeping in the car before but I'm pretty sure that neighbours would object to having a diesel engine running all night long
Edit:
Plus of course, as one gets older, one cannot handle the heat as well as we used to when we were teens, most of us oldies are carrying too much extra weight, I know I am and nothing seems to shift it either