I wear long sleeves long pants, dark blue, in hot sunny weather. Cotton of 65/35 mix wicks the sweat off to the outside to cool. White cotton/poly gloves. I'm never so hot as when I get sunburned. You have to get used to it. Turn up the airconditioning to 80 to get used to summer heat. Exercise outside often enough in heat, your capillaries open up. I learned to wrap up in the heat from my band director, that marched us 2 hours in the heat of Houston 5 days a week starting out in July, 65. That was on an asphalt training field. We had no water fountain available. After that I would walk home a mile. They would arrest teachers for training students like that these days. I weighed 110 lb those days, same height. Weren't any fat kids in our marching band. I'm 160 lb now, probably couldn't handle Houston anymore.
In heat if your heart starts racing or you stop sweating, or you get dizzy, stop right now and get in the shade or indoors. SIt down. Drink frequently. When I unloaded trucks in Houston summer heat 1970, I would sweat out and drink a gallon a day.