>>2670964Humidity aids in the conduction of heat, and usually not in the way you want. A humid hot area will cause heat injuries rapidly, and a cold wet environment will cause hypothermia rapidly. This is relative to a dry area of the same temperature and wind, of course.
Moisture can also cause its own problems (worsening terrain, reducing comfort, fog affecting visibility, etc.). Arid environments will cause you to dehydrate faster but are usually kinder to gear and will have less notable wildlife which is a net benefit unless you're there to fuck with animals.
