@B707 - I also live in a hot climate and do some running. I used to get so hot and sweaty before I discovered wicking material. The idea is that the fabric on the inside wicks moisture away from your skin and draws it to the outside of the fabric, where it evaporates. I have a couple of t-shirts that costs about $20 each.
Wicking fabric isn't just for athletes. Anyone who works outside like road crews, landscapers, police, or just anyone who wants to stay cool and comfortable, should try wearing clothing made from moisture wicking material.
Another really neat idea is to get these special wicking bed sheets. I've read that they work a lot better than cotton sheets to keep your body temperature comfortable. I hope I can afford to get some one day! They are a bit pricey.