Cold and Heat Exhaustion

Extreme Cold

Whenever the temperature is at or below 30 degrees Fahrenheit, a creature exposed to the cold must succeed on a Constitution saving throw at the end of each hour or gain one level of exhaustion (see table below). Creatures with resistance or immunity to cold damage automatically succeed on the saving throw, as do creatures wearing appropriate cold weather gear (thick coats, gloves, and the like) and creatures naturally adapted to cold climates.

(1) Disadvantage on physical ability checks, -10 movement.
(2) Being wet increases the saving throw DC by 10 and removes benefit of any cold-weather gear.
(3) Setting up a camp with tents and a fire protects you from the cold.
(4) Staying by a fire for 1 hour removes 1 level of cold-weather exhaustion.

Extreme Heat

When the temperature is at or above 100 degrees Fahrenheit, a creature exposed to the heat and without access to drinkable water must succeed on a Constitution saving throw at the end of each hour or gain one level of exhaustion. The DC is 5 for the first hour and increases by 1 for each additional hour. Creatures wearing medium or heavy armor, or who are clad in heavy clothing, have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw, as do creatures naturally adapted to hot climates.