# Extreme Cold *Environmental Hazard* When the temperature is 0 degrees Fahrenheit or lower, a creature exposed to the extreme cold must succeed on a DC 10 Constitution saving throw at the end of each hour or gain 1 [Exhaustion](Mechanics/CLI/rules/conditions.md#Exhaustion) level. Creatures that have [Resistance](Mechanics/CLI/rules/variant-rules/resistance-xphb.md) or [Immunity](Mechanics/CLI/rules/variant-rules/immunity-xphb.md) to Cold damage automatically succeed on the save. *Source: Dungeon Master's Guide (2024) p. 68*