put your shorts and shirt in the freezer for a bit before you set off, Ice cubes in the camelbak – plenty of fluids. I ofen also carry a cold bottle of water to tip on my feet as they seem to get very hot, and also tip into helmet and down back of shirt to help with cooling down.
Just be wary of overcooking yourself – your body core temperature needsto stay somewhere below 30 deg, once it goes above this you could start entering the realms of heat exhaustion. If it goes above 40 heat stroke could kick in.
For me its usually humidity thats the problem rather han just straight forward heat. I cycled around Cuba a few years back and away from the coast roads it was very humid and you just can’t seem to stop pouring with sweat. I think we used as much water to throw over ourselves as we drank.