The heat zaps me, too. I have to run any errands either really early in the AM or after the sun sets.
I remember (pre-MS) cutting the grass in 90+ degree temps.....then taking a shower and going out to supper!! That'll never happen now.....

.
I haven't tried any of the cooling vests or other things made for heat intolerance. I just stay inside in the A/C. Once the heat gets to me the fatigue, blurry vision and balance issues set in. Fun, fun.......