Short term - gas generator with A/C window unit. You could at least cool a sleeping room. We have the Honda Quiet which is extremely fuel efficient and is quiet enough to have a normal conversation while standing over it.
Of course if the SHTF is TEOTWAWKI, a running generator, no matter how quiet, would attract undesirables. Also, sources of gasoline would become depleted quickly.
Long term - Back to basics I guess. Wear light cotton clothing. Work only in the early mornings and late evenings. I have a couple of jell filled neck wraps that once re-hydrated are suppose to keep you (somewhat) cooler. I know I'll be sweating this extra weight off...for sure! :P
One of my concerns is the lack of ventilation in our communities. So many of us are packed into tight subdivisions that very little breeze can get through; not to mention the radiant heat from all the concrete and asphalt!
I guess there's a reason Houston's population exploded AFTER the invention of A/C. ;)
I read in emergencies, and this doesn't apply to total collapse, use the car a/c to cool off a few times a day. We have about 40 gallons in the shed...and of course 2 vehicles (mine) stay near full. Most don't think of their tanks as resources---I do. That's 36 gallons if both are full.
And we started our generator today---every month to be sure it's working.