In Western films like The Good, The Bad & The Ugly, Mad Max: Beyond Thunderdome, or even Knights of Cydonia there's a common theme of the danger posed by the desert heat, and characters struggling to make their way across the burning sands. While I tend to prefer the more basic rule systems for D&D, this was a case where I found the 3.5/d20 system had a good foundation that I could work with. Rather than use their entire ruleset for movement, heat and fatigue I've boiled it down (heh) to something I find more manageable.
This is the first part of these rules which deals with how the heat of the environment affects the characters in this campaign setting.
Heat
During the day characters outdoors are affected by heat, and may receive Fatigue Points.
Fatigue Points
Characters with Fatigue Points can not run and their Strength and Dexterity is considered 1 step lower (minimum of -1 on checks). If a character's Fatigue Points are greater than their current hit points, they fall unconscious. Any type of magical healing removes all Fatigue Points.
Medium or Heavy Armour
Make a CON check (d4/6/8 vs 4) each hour or take d6 Fatigue points. Reduce the CON dice (d4/6/8) by one step per hour to a minimum of d4.
Desert Travel and Mid-day Sun
Make a CON check (d4/6/8 vs 4) each hour or take Fatigue points - d4 for Regular Clothing, d6 for Light Armour, and d8 for Medium or Heavy Armour. Reduce the CON dice (d4/6/8) by one step per hour to a minimum of d4.
Unconsciousness
Characters who are unconscious and outdoors in the heat must make a CON check (d4/6/8 vs 4) each hour or take damage - d4 for Regular Clothing, d6 for Light Armour, and d8 for Medium or Heavy Armour. Reduce the CON dice (d4/6/8) by one step per hour to a minimum of d4.
Note on CON Checks
Ability score checks are based on a d6 roll with a target number of 4. If a character has an exceptional ability score this is reflected by rolling a d8 or a d4 instead.
