Heat deals subdual damage that cannot be recovered until the character cools off (by reaching shade, being doused in water, etc.).
A character who takes any nonlethal damage from heat exposure suffers from heatstroke and is fatigued. These penalties end when the character recovers from the subdual damage she took from the heat. Once a character takes subdual damage equal to his total hit points, any further damage is lethal damage.
A character engaging in moderate activity (marching, light labor) in very hot conditions (above 100° F) must make a Fortitude saving throw each hour (DC 15, +1 for each previous check) or take 1d4 points of subdual damage. The armor check penalty of worn armor (but not shields) applies as a penalty to this saving throw (the penalty is halved for non-metal armor). A character with the Survival skill may receive a bonus on this saving throw and might be able to apply this bonus to other characters, as well.
A character’s activity level, as well as the heat and terrain can change how frequently checks must be made. Light activity (riding, lounging) or shade reduce the frequency by one step. Heavy activity (combat, hard labor, sprinting), severe heat (120°+) and hazardous terrain (salt flats or obsidian plains) all increase the frequency by one step. The progression is:
| No check |
| 1/day |
| 1/hour |
| 1/10 minutes |
| 1/minute |
| 1/round |
