Drink plenty of water. It was pretty bad here this weekend at Blackhawk Farms for teh CCS races. Some people were starting to show signs of heat exhaustion. One racer apparently passed out and fell of his bike.
+1Remember to start hydrating the day or two before. If you neglect, you won't be able to drink enough water the day of.
I can't believe no one chimed in from Florida. Try Jennings, Homestead, PBIR and Otlanta, Barber. You want to talk about heat!! I understand that up north you guys are surprised by it for sure. I don't go to the those tracks between June and September. Talk about tire wear!!
I drink at least 1 1/2 gallon of water and lots of fruits, I raced MTB down here and hydrating the night before is super important.