I am about to bring my characters into the desert in my campaign, so I decided to read up on desert rules. From the Pathfinder SRD:
Heat deals nonlethal damage that cannot be recovered from until the character gets cooled off (reaches shade, survives until nightfall, gets doused in water, is targeted by endure elements, and so forth). Once a character has taken an amount of nonlethal damage equal to her total hit points, any further damage from a hot environment is lethal damage.
I am primarily used to 3.5e rules, so I didn't think much of this, until someone had reminded me that in Pathfinder, 0th-level spells work differently (emphasis mine):
Clerics can prepare a number of orisons, or 0-level spells, each day, as noted on Table: Cleric under “Spells per day.” These spells are treated like any other spell, but they are not expended when cast and may be used again.
Since create water is a 0th level spell, doesn't this mean that the characters can just be doused with water as often as needed, without penalty? As well, doesn't this mean that, despite requiring more water in the desert, it is still irrelevant because a cleric (for example), can just continually cast 'create water'?
EDIT
As a GM, is there anyway to make the desert dangerous in light of this? It's not very exciting to throw the PCs in a 'dangerous' area like a desert and have them avoid the hazards of the desert effortlessly. It also defeats the purpose of having extreme heat rules somewhat.