Drones feel no cold.
"And while the mountains are perforated with caves, any fire would stick out like a volcano to infrared detection, followed shortly thereafter with a GPS guided munition.
Instead of wandering in scattered parties, huddled around the campfire in caves. Invite a missile to dinner. Probably making them now to fly into the door and inside a ways before detonating.
Snow machine mounted patrols?
http://blog.wired.com/defense/2008/11/secret-rocket-b.html?happyfunball
This would warm the inside of the cave up real nice.