First where's your pc. Is it in the trunk? The trunk is one of the best places to put a pc. Do you have any case fans? I have a p2.4gh for my desktop, the more case fans the better. You can also use peltier element. These things are very effective for cooling a cpu. It looks like a white square. When you plug it in one side gets hot and the other side gets cold. Of coarse the cold side gets placed on top the cpu.
They say there's dangers with humidity, but if you have case fans blowing the air out. You really dont have a humidity problem. Also the higher the peltier wattage the hot side gets hotter, and the cool side geets cooler, and a higher humidity risk. Stick with an 80watt