These rules (taken from Delta, here, slightly modified) are important in a campaign like Arizona Adventures, with so much wilderness stuff going on, in a Dawn of Civ mileau, and such extremes of climate.
Rules for Exposure -
Characters lacking certain physical necessities accrue 1d6 damage per time unit, as outlined below (no savings throw):
--No Air: 1d6 per minute (starting when the air is cut off)
--No Shelter: 1d6 per hour (starting below 40 degrees and above 110 degrees)
--No Water: 1d6 per day
--No Food: 1d6 per week.
Under deprivation conditions, PCs suffer a -2 fatigue penalty to hit and AC, per unit of time, as well.