Editing DnD Desert Raiders Campaign Natural Hazards (section)

==== Steam and Mist ====
Although the waste is usually dry, circumstances can combine to produce thick clouds of mist or even steam. Some creatures living in such regions adapt and become able recover the precious moisture from the atmosphere.
Deserts that border coastal areas do not themselves receive much precipitation, but when cooler, moist ocean air encounters the superheated air over the land, water condenses out into a thick mist. During the day, this mist is uncomfortably hot, while al night it is more tolerably warm until it is dispersed by strong winds that kick up as the land cools. In active volcanic regions, hot springs and fissures vent scalding stearn. Lava flowing into a body of water throws up huge clouds of hot mist, as well as showers of stone fragments and ash.
Areas of hot mist increase the effective temperature band by one (see Table 1-1, page 12), as humidity combines with high temperature to keep the body from cooling during the day and conversely moderates the cold of the desert night.
Steam erupting directly from a hot spring, lava flow, or other fiery source is much more dangerous, dealing 1d6 points of lethal damage per round to a creature within (no save). Such steam does cool rapidly in the air, however, and only deals such damage within a 30-foot radius of its fiery source. Beyond 30 feet from the source, the steam is just a warm mist.
Mist or steam obscures vision, providing concealment. If it contains dust, powdered salt, and similar noxious substances, mist also poses the risk of suffocation (see page 304 of the Dungeon Master’s Guide), Toxic vapors mixed with fog acts as an inhaled poison.