Cold Weather, Sleep & Hypothermia

Start With the System

Protect the body's heat faster than the environment removes it Cold stress is a systems problem involving shelter, clothing, food, hydration, workload, wind, moisture, ground contact and sleep. The safest plan prevents heat loss early and treats persistent shivering or altered thinking as operational emergencies.

Core principles 2 First-hour priorities

• Stay dry from precipitation and sweat; moisture strips insulation and • Establish a dry sleeping platform and deep ground insulation before accelerates heat loss. improving comfort elsewhere. • Insulate from the ground as aggressively as from the air. Compressed • Create dry and working clothing categories; protect sleep layers bedding loses performance. from sweat and rain. • Block wind while preserving enough ventilation to control • Stage fire-starting, water, light and footwear so a nighttime problem condensation and combustion hazards. does not require disorganized exposure. • Eat, hydrate and schedule work so the body can produce heat • Set a pre-sleep routine: eat, drink, urinate, dry feet, adjust layers and without soaking clothing. inspect shelter ventilation. • Recognize cold injury early and seek emergency care for severe or • Create clear thresholds for stopping work, rewarming, requesting worsening symptoms. help or evacuating.

Warm air is not enough. Wind, wet clothing and ground contact can Do not use open flame or unsafe combustion inside an enclosed shelter. overwhelm a small fire and a good attitude with equal efficiency. Carbon monoxide is colorless, odorless and deadly.

Field Rule

Persistent shivering, clumsiness, confusion, slurred speech, unusual behavior or declining consciousness are not endurance tests; they are reasons to stop, shelter, rewarm and seek emergency help.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 2

Choose Deliberately

Heat-loss control matrix Control all major paths of heat loss. Improving one while ignoring another can create a false sense of safety.

Heat pathway Field example Primary control Inspection question

Conduction Sleeping on cold ground, wet logs or metal Deep dry ground insulation and raised platform Is bedding compressed, damp or too thin under hips and shoulders?

Convection Wind stripping warm boundary air Windproof shell, tight shelter skin and protected Where can moving air reach clothing entrance or sleep system?

Evaporation Sweat, wet clothing, breath and damp bedding Pace work, vent layers and dry equipment Did work create moisture faster than the system can remove it?

Radiation Heat lost from exposed body and large shelter Insulation, hat, smaller protected space and Is unnecessary volume being volume reflector used safely heated?

Respiration Cold dry air and high exertion Moderate pace, face protection that does not Is heavy breathing driven by obstruct breathing avoidable overwork?

Fuel deficit Insufficient food and dehydration Regular calories, warm fluids and planned Is declining warmth actually an reserves energy problem?

Sleep disruption Cold spots, wet feet, fire tending and anxiety Reliable bedding, dry layers and a nighttime plan Can the system maintain safe rest without constant crisis work?

Decision note: Test the sleep system in controlled conditions colder, wetter and windier than expected, with the clothing and body position you will actually use.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 3

Repeatable Beats Heroic

Cold-night sleep workflow A safe night is built before darkness. Sequence the work so shelter, bedding, fuel and dry clothing are protected while energy is still available.

Secure the Shelter Envelope

Repair leaks and drafts, manage drainage, protect ventilation and reduce unnecessary interior volume.

Build the Ground System

Create a dry platform and enough loft to prevent hips and shoulders from compressing insulation to the ground.

Dry and Stage

Change out of wet work layers, dry feet, protect sleep clothing and stage boots, light, water and fire tools.

Fuel the Body and Camp

Eat an appropriate meal, hydrate, prepare safe fuel and eliminate tasks that would force unnecessary nighttime exposure.

Monitor and Respond

Check cold spots, moisture, shivering, thinking and partner behavior. Rewarm early and activate emergency plans when symptoms progress.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 4

Adapt Before Conditions Force IT

Cold-weather operating scenarios Different cold problems need different corrections. Wind, wetness, ground contact and metabolic fatigue are not interchangeable.

Wet cold near freezing 2 Dry extreme cold

• Prioritize rain protection and sweat control. • Protect exposed skin and extremities.
• Change or dry wet base layers before rest. • Manage breath moisture near sleep insulation.
• Increase airflow around bedding while keeping precipitation out. • Use deep loft and minimize compression.
• Use smaller work cycles to avoid soaking insulation. • Warm tools and boots carefully without fire damage.
• Treat persistent dampness as a shelter failure. • Schedule frequent self-checks for numb or pale tissue.

Wind event 4 Nighttime decline

• Inspect anchors, roof, entrance and tree hazards early. • Stop and assess shivering, speech, coordination and thinking.
• Move work and storage into protected zones. • Replace wet clothing and add insulation from ground and wind.
• Eliminate loose clothing and gear that can snag. • Use warm sweet fluids only when the person is alert and can
• Reduce trips outside. swallow safely.

• Maintain ventilation even while sealing drafts. • Handle gently and avoid unsafe direct heat.
• Request emergency help for severe or worsening symptoms.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 5

Diagnose the System

Failure modes and corrections Cold systems often fail gradually: a damp layer, compressed bed, low food intake and one windy hour combine until judgment declines. Early correction is far easier than rescue.

Failure signal Likely cause Best correction

Cold hips or shoulders at night Compressed or insufficient ground insulation Add dry loft under pressure points and widen the insulated platform.

Bedding becomes damp Sweat, breath, ground moisture, leaks or poor Identify the moisture source, vent, dry and protect the sleep ventilation system.

Hands or feet stay cold Wetness, constriction, low activity, poor insulation Dry, loosen, insulate and rewarm; assess for cold injury. or systemic cooling

Shivering returns despite fire Wind, wet clothing, ground loss, low fuel or Move to shelter, replace wet layers, insulate fully and seek progressing hypothermia emergency help.

Morning gear is frozen Moisture trapped in boots, gloves or clothing Dry earlier, store strategically and keep critical items from saturating.

Thinking and coordination decline Cold stress, exhaustion, dehydration or Stop work, shelter, rewarm, communicate and activate evacuation hypothermia criteria.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 6

Carry the Standard

Cold-night readiness and symptom card The purpose of the sleep system is not merely comfort. It preserves judgment, coordination, immunity, recovery and tomorrow's work capacity.

FIELD CHECKLIST STOP / REASSESS

Persistent or violent shivering, or shivering that Weather, wind, precipitation and overnight low reviewed. stops despite continued cold. Shelter leaks, drainage, ventilation and overhead hazards checked. Confusion, apathy, slurred speech, stumbling, poor coordination or unusual behavior. Ground insulation remains deep and dry. Waxy, pale, hard, numb or blistered skin. Sleep clothing is clean enough, dry and protected. Unsafe indoor flame, stove or combustion with Wet work layers separated and drying safely. inadequate ventilation.

Food and hydration completed before bed. Person cannot swallow safely, becomes drowsy or loses consciousness. Fire and combustion plan is safe and ventilated.

Boots, light, water and emergency gear staged.

Hands, feet, face and skin inspected for cold injury.

Shivering, speech, coordination and thinking assessed. AUTHORITATIVE STARTING POINTS Night checks and partner checks scheduled when appropriate. CDC - hypothermia and cold weather https://www.cdc.gov/winter-weather/about/about-h Evacuation and communication thresholds remain clear. ypothermia.html

National Weather Service - cold safety https://www.weather.gov/safety/cold

Wilderness Medical Society https://wms.org/

American Red Cross - first aid https://www.redcross.org/take-a-class/first-aid/perfo rming-first-aid/first-aid-steps

Cold injury and hypothermia are medical emergencies. This guide supports prevention and recognition but does not replace emergency services, medical assessment or professional wilderness-medicine training.

Education and planning reference. Verify current laws, rules, medical guidance, and local conditions. 7