Staying Hydrated
With the heat and humidity brings proper preparation as far as fluid intake. If competing tomorrow your extra fluid intake should start now at least 24 hrs. before your event. During the race under these conditions means drinking every 10 minutes when racing. Another thing to consider, is to have a person set up in the "feed zone" usually at the top of a hill to hand you a water bottle.
Don't try a new product in your water bottle without tying it well before hand. I tried straight Gatorade once before a race and regretted it ever since. Now I dilute it with 50% water, 50 % Gatorade. Adding a product like Saltstick caps which is a buffered electrolyte salt to your intake during and after competition can also help with cramping if you sweat a lot.