Cold weather survival means surviving exposure to cold and the military training directed at that task. Isolated personnel must preserve body heat, mobility and judgement with the resources actually available to them. During evasion, this includes protection while resting in concealment and allocating work, food and water so that further evasion remains possible. The German term Winterüberleben also includes wet, windy cold without snow.
Cold and functional ability
Heat is lost through several routes: wind carries heat away from the body's surface, cold ground takes heat through direct contact, and evaporating water consumes heat. The body also radiates heat towards colder surrounding surfaces. Wet clothing insulates less effectively than dry clothing. A person can therefore become dangerously cold above freezing, particularly after rain, contact with water or heavy sweating.
In the cold, the body reduces blood flow to its outer regions to retain heat in the core. Hands and feet cool as a result; fingers lose dexterity and muscles can become stiff. Opening a fastening, putting on more clothing or handling small items of equipment then takes longer. Gloves provide protection but also make some precise movements harder. Necessary tasks should therefore be prepared while the hands still function, and work on small items with bare hands should be kept brief.
Using available protection
When movement gives way to rest, the heat produced by muscular work falls away. Before a prolonged observation or concealment period, clothing is therefore closed again or supplemented with available layers. The resting place needs protection from wind and precipitation and separation from the cold ground. A dark, well-concealed hollow may be wet or intensely cold; visual concealment does not solve its thermal problem. The effort of reaching a better place must be weighed against the movement required and the strength remaining.
Available dry clothing, a mat, a blanket or other suitable insulation is used where heat is being lost: beneath and around the body. An available weatherproof covering blocks wind and incoming water; insulation beneath it slows heat loss. A thin sheet can limit wind exposure and evaporation; reducing heat loss to the ground requires additional insulation. Dry leaves, dry moss or boughs can form an insulating ground layer even without a manufactured mat. Collecting, cutting and carrying them nevertheless requires work and leaves changes at the site.
Wet clothing is replaced with dry clothing when dry replacements and sufficient protection during the change are available. Without replacements, an impermeable covering that is actually available can limit evaporation and wind exposure for a resting person; available insulation and ground protection are still needed. The covering produces no heat. This measure to limit further losses is also no reason to continue a strenuous march permanently sealed inside it: further moisture would accumulate beneath the covering.
Work, rest and supplies
Work rate and clothing are adjusted before heavy sweating develops. During strenuous movement or work on protection, available layers can be opened or reduced while retaining protection from wind and wet conditions. Snow on clothing is removed before it melts and wets the material. A person building protection at maximum speed may initially feel warm and then cool rapidly on stopping. A shorter period of work followed by another check of wetness, warmth and strength can therefore allow more useful rest than a major construction effort.
Muscular work and shivering consume energy. Food and drinkable water must be considered for the onward route as well as for work at the resting place. Cold blunts thirst even though fluid is lost through sweating and breathing. Available food and water should be used with as little additional work as possible; further procurement requires time and strength. If melting snow for water or preparing available food requires a heat source, fuel use and the risk of detection are added.
Warmth and detection
Additional journeys to collect material or fuel create tracks in snow that can lead to the resting place. Fire provides warmth but also produces light and smoke; in severe cold and still air, smoke can remain above a site. Heat also contrasts with a cold background. A decision to use a heat source therefore includes its actual benefit, the work required and possible observation. A white camouflage pattern changes visible colour but does not remove a temperature difference.
A long, motionless period in concealment reduces revealing movement but increases the risk of cooling when insulation and weather protection are insufficient. Conversely, constant movement can consume the strength needed for a later essential journey and make the route more evident. Before stopping, the person therefore checks whether their resources allow them to rest there, and during the halt whether hand function, attention and mobility are being maintained. A place where these abilities keep deteriorating loses its value for further evasion.
Warning signs and decision limits
Increasing clumsiness, memory lapses, confusion, slurred speech and drowsiness may indicate hypothermia. The person may no longer recognise their deterioration reliably. Shivering produces body heat; its decline despite further cooling is no reassurance. Repeated failure at simple manual tasks or difficulty understanding the next step are reasons to avoid additional exertion and limit heat loss in the most sheltered place practicable. Available dry covering and insulation then take priority over further extensive construction or a long, demanding onward journey. When fully awake, the person can use available food and a non-alcoholic drink. Alcohol, rubbing the limbs and uncontrolled intense heat are unsuitable countermeasures.
Local cold injuries particularly affect feet, hands and exposed parts of the face. Wet, cold feet can be injured without freezing; tight lacing and prolonged immobility worsen the problem. Overly tight lacing is therefore loosened, and damp socks are replaced with available dry ones. During a sheltered halt, the feet are dried and protected from further wetting as far as this is possible without additional cooling. Pale, waxy, unusually firm or numb skin is a warning sign of frostbite. Affected areas are protected and not rubbed or worked with snow. Frozen tissue is not deliberately thawed while refreezing remains possible, because that cycle causes further damage. Walking on frostbitten feet adds stress to damaged tissue; an immediately necessary evasion movement has to be weighed against this worsening injury. Face camouflage paint can conceal pale colour changes, making developing frostbite harder to recognise.
National training uses
In Norway, the NATO Winter Survival Course is directed at air personnel and covers tasks including movement in snow, emergency bivouacs, food, water and communicating one's location after an aviation emergency. The training aim is to remain functional until recovery and become locatable. The NATO Cold Weather Survival Instructor Course has a different emphasis: instructors and advisers learn to survive behind enemy lines with minimal equipment and prolonged interruption of supplies. It is primarily intended for officers and non-commissioned officers assigned to long-range reconnaissance and special operations. In that situation, warmth and supplies have to be reconciled with concealment from the enemy; open visibility to searchers would be a different objective.
Canada's Arctic Aircrew Survival Course focuses on aircrew survival priorities in Arctic conditions, particularly emergency shelter and maintaining body temperature. The survival equipment that can actually be reached depends on the aircraft and the emergency. An earlier Arctic course therefore included practical use of the smaller equipment carried in an ejection seat and the different equipment carried in larger aircraft. For isolated personnel, this means using the functions of available materials and avoiding plans for protection or supplies that depend on items left behind when leaving the aircraft.
An earlier Finnish SERE instructor-course model combined an autumn C phase with a separate winter SERE phase. Its subjects included survival and movement in enemy-controlled territory, conduct after capture, personnel recovery and using personal equipment and the environment. The winter component thus carries survival and movement tasks into cold conditions. Sweden's winter unit at Norrbottens regemente also trains regular units for combat, specialist functions and movement in subarctic conditions. Such winter training covers the functional ability of entire units and their equipment; cold weather survival during isolation centres on the person and the resources remaining to them.