"Well if you are in a desert enviroment then warmth is something to shield you from (rather than what you need) and water is more important."

Correct, up to a point. Many are surprised to realize that deserts can become bitterly cold - rapid diurnal swings resulting from low humidity. elevation plays a role, as well.

In Tucson, AZ,temps into the 20F range were not at all uncommon, and even colder has been endured. Of course, it does warm up and get nice and toasty during the day.

Water is indeed very important, in ways that might surprise you. In my time in SAR in southern AZ, the number two cause of death was crowning, just barely surpassed by falls. Flash floods and high wter are real killers.