Trudging through deep snow for hours on end, or facing biting, bitter winds, can dehydrate and fatigue a character as quickly as blazing deserts. Every four hours spent in weather below freezing (32° F), a character must make a Vigor roll. Failure means the victim gains a Fatigue level. Subtract 1 from the victim’s Vigor roll for every 20 degrees below freezing to a maximum of -3.
The roll assumes the character is wearing warm clothing. If not, subtract 2 from the total. Modern winter gear adds +2, and advanced gear (arctic suits) add at least +4 or more depending on the setting.
Savage Worlds Deluxe Edition p. 99