Extreme Heat
CON save each hour (DC 5 + 1/hour) or gain exhaustion. Disadvantage in medium/heavy armor. Fire resistance = auto-success. Double water needed.
Temperatures at or above 100°F (38°C) present a serious hazard to unprotected characters.
Saving throws: A creature exposed to extreme heat without access to water must make a Constitution saving throw at the end of each hour spent in the heat. The DC starts at 5 and increases by 1 for each subsequent hour.
On failure: The creature gains one level of exhaustion.
Modifiers:
- Creatures wearing medium or heavy armor or heavy clothing have disadvantage on the saving throw.
- Creatures with resistance or immunity to fire damage automatically succeed.
- Adequate water supply reduces risk (DM discretion on exact impact).
Cumulative danger: Because the DC increases each hour and exhaustion stacks, characters can deteriorate rapidly. After 6 hours without relief, the DCs become quite high (DC 10+), and multiple levels of exhaustion severely impair the character.
Water requirements: In extreme heat, characters require 2 gallons of water per day (double the normal 1 gallon). Going without adequate water in heat triggers dehydration faster — exhaustion after half a day instead of a full day.
DM tips: Extreme heat is most impactful as a multi-hour travel hazard. It pairs well with water-scarcity scenarios, desert exploration, and volcanic environments. The create water spell and Outlander's Wanderer feature can mitigate these hazards.