I've worn level II vests with trauma plate for a living for the last decade in fine Dallas heat... Notice I said vestS, since I'm currently on my third. Human sweat and the nasty stuff that's in it doesn't play well with most things. You just don't notice what it does to your clothes since most people don't wear the same shirt every day and get it completely soaked with sweat. If you did, it would fall apart pretty quickly. Since Dallas is great for sweat production, I retire my vests faster than the suggested rate. I've also got four sets of carriers for it since they get super nasty super fast and I'm not about to do laundry every day. It's not a cheap investment, especially when you factor in other costs like all the various powders, sprays and "miracle" products you are going to try out to keep your skin from falling off in one giant sheet, or to get rid of the rashes and sores you will develop.
If you guys want to know what it's like to wear body armor in the south... get two thick sheets of cardboard and duct tape them to your body front and back. Now, wait for the temperature outside to get to about 110 and go jogging. Yes, yes, it's not always 110 degrees out... but, wearing body armor will raise your core body temperature 10-20 degrees. So, a 90 degree day out means that your torso will be feeling like it's 110. Get a day that's really 110 out and that means your cooking. Yeah, the guys coming back from the sandbox won't be so impressed, but most people on here really never think about that.
The other thing no one ever thinks about until after they try wearing armor... it's a nasty sponge. Wear what ever expensive t-shirt you want, by the end of a shift you are a smelly soggy mess. It's like wearing a nasty sponge that's been sitting in your sink too long. And since you are wearing the nasty sponge that's been sitting in your sink too long, you will smell like a nasty sponge that's been sitting in your sink too long... even after you've tried every spray and powder on the market and have four different carriers.