If you are trapped in the wild, that would count as an emergency. In that case, you may want to signal for help by flashing a mirror, building a smoke signal by burning green wood or leaves, and yelling for help when you hear passersby. If you have to build a fire to keep yourself warm, you should do that. Also, insulate yourself from the ground while sleeping by placing pine needles or other material beneath you while sleeping, because you lose more body heat from the cold ground than from the cold air.