If anywhere in the world has figured out how to dress for heat and humidity, it's the Indian subcontinent, and all I'm saying is the sari involves bare midriff for a reason. I live in the southeast and spend a lot of time outside. To cut down on my sunscreen bill, I've started wearing loose, long sleeve white cotton button ups with the last few buttons undone so I can tie the ends up around my waist.
You catch a breeze wearing that, and it's like wearing a weightless AC unit on your back. Hand to God.