"Everyone is used to it" Idk, seems to scale a bit with body weight in my experience. I know Texans and Arizonans that don't mind the heat and others that detest it.
All I know for sure is there is a certain level of hot you can reach and clothing, ego, cultural pride, all that goes right out the window. Or you die. Drinking water only goes so far. And that kind of climate is in the mail for p[arts of the South.
I lived in Qatar for awhile, developed quite a heat tolerance. Only time I could ever wear jeans was at night on camping trips out in the desert. I still can't believe Wahabi Arab women wearing the head to toe, pure black niqab. Making women walk around in those July-August always felt like a hate crime to me. Like why you guys cook your women so much? Always felt bad for them.