Shelter and an unplanned night outside

Choose a safer site, stop conductive and wind-driven heat loss, and make darkness manageable.

General field reference, not medical advice. Use it to support immediate decisions, then follow 911, rescue coordinators, medical professionals, current warnings, and local agency guidance.

Act now

1. Stop before darkness removes safe site choices.

2. Get out of wind, precipitation, moving water, avalanche paths, and falling-tree hazards.

3. Insulate every person from the ground.

4. Replace or cover wet clothing and protect head, hands, and neck.

5. Make the shelter visible without placing it in a dangerous location.

Choose the site before building the shelter

A shelter cannot compensate for a hazardous site. Avoid drainage bottoms that can flood, exposed ridges, gullies below loose rock, avalanche terrain, standing dead trees, fire-damaged timber, and low pockets that collect cold air when a safer nearby option exists.

Look up before settling down. Wind, snow, and rain can bring down branches and weakened trees. Keep distance from cliff bases, unstable slopes, and water that may rise overnight.

Control the main paths of heat loss

• Conduction: Use pads, packs, spare clothing, branches where lawful, or other dry material between the body and cold ground.

• Convection: Block wind and close unnecessary shelter openings while maintaining safe ventilation.

• Evaporation: Replace wet layers or isolate them from dry insulation. Protect from rain and sweat.

• Radiation: Add dry insulation and cover exposed skin.

Ground insulation is often as important as the roof. A waterproof layer overhead with a body directly on cold ground may still fail.

Use simple shelter layers

The safest emergency shelter is usually equipment carried for that purpose: bivy sack, tarp, rain gear, insulated clothing, and a sleeping pad. If improvisation is necessary, favor a small windproof and waterproof space that can be built without injury or major energy loss.

Ventilate any enclosed shelter. Never operate a fuel-burning stove, lantern, heater, or charcoal device inside a tent, vehicle, camper shell, snow cave, or other enclosed or partly enclosed space unless the appliance and structure are specifically designed and installed for that use.

Manage the night

Ration battery power, but keep a light accessible. Organize water, communication equipment, footwear, and essential clothing so they can be found in darkness. Set check intervals for weather, patient condition, and shelter stability.

If the group is expected by rescuers, avoid moving at first light without communicating unless the shelter site becomes unsafe.