Don't know if your sensitivity to heat is simply a matter of dislike or sensitivity to heat related illnesses.
I have given a lot of seminars teaching people about heat stress / exhaustion as a manufacturer in equipments that monitors personal heat stress. While my focus has always been related to industrial and occupational application, heat related illnesses are all the same.
Without getting into technical details you need to get rid of as much heat as your body receives or creates. Naturally the body only has one (significant)way to regulate that - perspiration.
Number 1 is to allow that to happen, i.e. by exposing as much skin as possible (
consider social factors here - I have heard some rumors I have heard about BM's excessive use of dental floss thongs) by wearing cotton t-shirts and shorts. If you body does not release water through the skin (sweat) well you can add some your self.
Number 2 is to properly replace the fluid loss from the perspiration. Water alone is at best only a reasonable solution. You also need to replace the electrolyte (salt) loss and preferably drink an electrolyte replacement drink that contains potassium. Gatorade or Powerate are both much better than water, but are limited in potassium. In the industrial market there are a few optimized drinks, such as Sqwincher, which include potassium, etc., however, for hot/humid weather conditions any of the above (and similar) drinks will do you good.
Other issues to take note of is limit metabolic heat production (exercise) and alcohol (
). Finally, if you are experiencing heat stress/exhaustion don't drink your fluid too cold, it may fool the hypothalamus and could limit the perspiration rate that you are trying to accelerate.
An OT side note (totally contradictive to the topic at hand): Mixing alcohol with an electrolyte replacement drink (i.e. vodka and Sqwincher) will accelerate the introduction of alcohol to the blood stream and get you drunk faster.