You should only expect to survive threes hours without shelter.
Hypothermia can kill you in just a few minutes and it catches fast, according to John Heatherly, author of The Survival Template. Assuming you’re away from a car or other pre-made shelter, you’ll need to build your own—and fast.
“If you’re in an unknown situation… shelter is your first priority,” said Heatherly.
The word “shelter” conjures images of wooden cabins, straw huts or elaborate tree houses, but in reality shelter can be as simple as a collection of debris, similar to a squirrel’s next.
“[Eighteen] inches of leaves will keep you warm in 32 degree weather,” said Heatherly. “The key is creating dead airspace. The more you have, the warmer you’ll be.”
If you have a tarp, Heatherly said the simplest and quickest kind of shelter to construct is a tarp shelter, but if you don’t have supplies, a debris shelter is efficient and can be made out of leaves, branches and dirt.
“If you’re stuck and don’t have equipment, a debris hut is a fabulous shelter,” said Heatherly.
In a survival situation in snow, the main objective is to stay dry, which can be a challenge. Caves can be dug out in the snow, shelter can be taken under trees large enough to have a dry area on the ground. In an ideal situation where tools are available, Heatherly said you should dig as deep
into the snow as you can without getting wet, build a fire circle within the shelter and create a lean-to with a tarp.
In a survival situation, shelter should be rated among your top priorities, if not the first. Without it, you won’t survive.