As someone who grew up in hot, Southern summers, I will say that it is a whole different ball game here than in other areas of the country. Even someone from Arizona, where temperatures on the thermometer reach way higher than they do here, can't handle the heat in the South. It's the humidity. It makes you feel like you are wearing a winter coat the second you step outside. It weighs you down and saps all of your energy.
Pro Tips from a humidity pro:
Wear light clothes. Less clothing does not necessarily mean you are going to be better off. Wearing very light, long sleeved clothing will give you added sun protection while keeping you cool.
Give up on your hair. It's just not going to look good. Everyone is in the same boat, so no one else cares, I promise. Get a good hat and wear it during the day. Also give up on your make up, ladies. It's going to come right off.
Drink lots and lots of water. Bonus trips to the bathroom mean you are spending more time in the A/C, right? You need more water than you realize, because you are sweating... a lot. Sweating is gross, but it helps keep you cool and honestly if you aren't sweating you're in trouble. Wear some deodorant and keep some moist towelettes with you to freshen up throughout the day.
While on one of your numerous bathroom breaks from tip 3, run cool water over your wrists. Instant refresh!
Avoid the parks during the middle of the day. I promise you aren't missing out on any fun from 11-3 and you'll be happier for the break. Go tour a resort you haven't been to yet or catch a movie. Summer evenings are where it's at.
Sun. Protection. You know what's worse than humidity? Being sunburned in the humidity. Wear sunscreen, clothing with SPF benefits, hats, sunglasses, and more sunscreen. Seriously.
It's not the face of the sun... That is probably more comfortable! But really, as long as you are smart about hydration, sun protection, and staying inside during the hottest part of the day you won't have any problems.