So, since a few people have asked about if I'm doing rules for heat and such...<br/><br/>What I'm planning on is, this world is one that's used to people going down to the surface to work, sometimes for days at a time, and lifestyles and technology have adapted to such.  The PCs also know what they're doing, even if this is the first time they're going down to the surface, there's plenty of people to teach them what they need to bring with and what they need to do.  So, I'm assuming the party always takes enough "generic desert supplies" to last for whatever length they plan on staying on the surface, plus two or three days extra in case of delays - this includes salves and potions to resist heat, something to provide shade, metallic paint to make armor reflective and not absorb sunlight, and so on.<br/><br/>If the party gets stranded however, then I'll start enforcing heat and survival rules, probably using the Sandstorm D&D book for part of it.  To keep things simple, I'm just going to say that everyone's heat-resistant supplies run out at roughly the same time, so there's no point in "stocking up" with more of the items from the book (the idea is that you did stock up ahead of time with your desert supplies), and I'll just be handwaving the costs of everything so there's not much of a need to find the book if you're not familiar with it.