Artoomis said:
We are talking about PROFESSIONAL ADVENTURERS. They can generally rest anywhere, under any conditions, much like modern day soldiers do.
The only exception really should be very harsh condtions, like a outdoors in a raging storm or the like.
Give your PCs a break.
The problem with this answer is that it could be applied to any question requesting a DC: What is the DC to hit an ogre? Come on, these guys are professionals! Of course they can hit an ogre. What is the DC to find this trap? Hey, this is a professional rogue! Of course he finds the trap! What is the DC to resist this spell? We are talking about PROFESSIONAL ADVENTURERS. Give your PCs a break.
D&D may not be a
simulation, but that does not mean that some players do not enjoy
simulating a simulation, if you take my meaning.
Trying to get a good night's sleep, under some circumstances, may well be treated like a hazard. The consequences of failing when confronted by that hazard are in the rules. Why couldn't this be part of an adventure?
What one would want to do is determine a baseline first, the outmost conditions under which no check was required within a given campaign. For example, is it your decision that PCs should have to roll a check if they are sleeping in a dungeon? If not, why not? What about outdoors without gear in warm weather? Etc., etc.
Once you have an idea where the cutoff is, call it DC 5. I'd say give the player the choice to make a Fort save or a Concentration check (whichever is better). Then consider how much more difficult circumstances are from your baseline, and add modifiers appropriately.
JMHO, of course.
RC