Some people are unfortunately just naturally heat intolerant. My advice: 1. JanJan and Rapunzel's advice is good to (a) acclimatise before the race and (b) to check yourself during the race. 2. Sweat produces moisture which the wind then evaporates which cools you down (Evaporation is a endothermic reaction so it pulls heat out of you.). Therefore, if you do not sweat much, throw water over yourself to evaporate which will cool you down (this is MUCH more effective than drinking more water to try to cool down). This is most effective in hot, dry conditions - less effective in humid conditions since the water will not evaporate as quickly. Also see this advice from running a marathon in the heat (and cold & rain) - this should equally apply to cycling in those conditions: http://running.competitor.com/2013/10/training/marathon-prep-running-in-bad-weather-conditions_85653 Some background to this advice: I used to work on the mines and there it could be very dangerous if one's body does not adapt to the heat (specifically in the deep gold and platinum mines). The mines then use a Heat Tolerance Test" to determine which individuals are "heat intolerant", and which are not. One could fail the test if you are even slightly sick, or suffering from a hang-over, thus the mines allows you to come back once or twice to be re-tested if you fail the test. If you failed the third time, you are redeployed to cooler working areas. See this article about AngloGold Ashanti: http://www.anglogold.co.za/subwebs/InformationForInvestors/ReportToSociety04/values_bus_principles/safety_health/sh_cs_sa_7_12.htm Another area where heat tolerance is critical is when one wants to join the Mines Rescue Services (Proto teams) - These teams go in when there is trouble and they sometimes work in very hot temperatures (sometimes putting out underground fires). As such, their Heat Tolerance Test is a bit more onerous than the "normal" test - you "work" for 1 our in a hot, humid environment (32 / 34 degrees). Unfortunately fitness has nothing to do with heat tolerance. I was reasonably fit when I took the MRS HTT and still failed it dismally - my temperature went up to > 40 degrees (has to be below 39 degrees to pass), despite me feeling OK during the whole test (I also sweated the least of all the participants). They immediately treated me for heat stroke and had me checked up by a GP before allowing me to go home. They even made me sign a document that I will NEVER again attempt to pass an HTT again... The mines also uses an acclimatisation process for people that were off the mine for a week or longer to make sure they adapt to the heat. When I was very hot underground, I would pour water over me and find an intake airway (where the wind effect is quite strong - best way to cool down). Hope this helps.
