Hiking through winter forests is exhilarating, at least until the snow starts to fall with a vengeance and there’s no shelter. Heavy snowfall, wind gusts up to 40 mph, a whiteout in which the horizon disappears and there are no reference points to count on: A blizzard is a hiker’s nightmare, especially if you’re caught unprepared.

Getting stuck in a blizzard in the woods means you have to think, and act, fast. Here’s what wilderness experts recommend.

Related: Survivorman” Les Stroud: What to Do If You’re Lost in the Wild

Gimme shelter

Create a snow shelter. If you’re stuck in a blizzard without even a nearby vehicle and hiking to safety is not feasible, experts says it’s crucial to create a snow shelter immediately. Otherwise, the authors of the book “The Extreme Survival Almanac” warn, “you may wander in circles, stumble into dangerous shallows or icy slopes, or just burn up all your energy and freeze to death.”

Here’s what the authors recommend if you’re caught in a blizzard in snow country.

  • Build a sort of igloo in the snow using a shovel or other digging tool (such as a stick) or create a shelter out of a snowdrift.
  • Cut a small hole in the roof to prevent the build-up of carbon monoxide. It should be a few inches across and at a 90-degree angle to the prevailing wind. String a shoelace between two sticks for a makeshift snow cutter if necessary.
  • Make a “door” with a tarp or branches, but be sure it’s at a 90-degree angle to the prevailing wind or wind and snow will swirl around your shelter or — worse — block your entrance.
  • Poke a smaller hole through the side of the shelter that faces the “door” to allow for cross-ventilation.
  • Keep a sharp stick inside the shelter to clear snow out of the ventilation holes whenever it builds up.
  • Leave the entrance open whenever a fire is going, and build the fire near the entrance hole.
  • If you’re with someone and have a fire going, watch each other for signs of carbon monoxide poisoning.
  • Keep the roof low and your bed high.
  • Never sleep on the snow — it will rob you of body heat. Pile branches, grass, moss, pine needles or even sticks or rocks inside your shelter to use as a bed and keep dry.
  • If you’re with someone, sleep close together to share body heat.

Hang a snow-filled bottle near the roof to melt snow into water. If you are able to build a fire nearby, keep it small — you don’t want the walls to get too mushy.

If there’s not enough snow, create a make-shift lean-to. If there’s a blizzard but not enough snow on the ground to build a snow shelter, the authors suggest throwing together a lean-to shelter from whatever materials you have. If you have rope and a tarp, you can quickly string up a makeshift tent by running a rope between two trees.

If you don’t have a tarp or rope, huddle under the branches of a low-hanging tree or quickly gather branches and lean them at a 45-degree angle against a tree or rock. Weave them together with more branches and cover it with grass or more branches for a thicker “roof,” then throw some pine needles and more branches inside for bedding.

Build a fire. Try to start a fire close to large rocks that will reflect heat. Gather wood and kindling quickly before your fuel gets wet from the snow. (Wrap that compact tarp in your trunk or backpack over the fuel to keep it dry as possible.)

Stay as hydrated and warm as possible. “Whenever you’re working hard, you’re building up a sweat, so you need a layering system for clothes,” says Andrew Dudik, an outdoor equipment expert at GearX.com and certified winter emergency medical technician in Burlington, Vermont. “If you get hypothermia, you’re in real trouble. As you get colder and colder, you lose motor functions and mental functions and you need all of that to stay healthy and sliding further down the scale.”

Dudik also offers these tips:

  • Keep your body covered. Always wear a hat and gloves to reduce heat loss.
  • Melt snow before consuming.
  • Exercise to stay warm and maintain circulation, but not hard enough to break a sweat.
  • Stay in one place as long as practical and safe. Walking in deep snow can wear out the body quickly, while sweating from exertion can cause chills and hypothermia.

Related: What to Do If You Get Lost in the Mountains

Signal for help. When it stops snowing, make a giant signal outside your shelter – perhaps spell out “HELP” with rocks or bright clothing — so aerial rescuers can spot you.

Preparing for a blizzard

Although meteorologists are often able to broadcast blizzard warnings hours or even days in advance, furious storms can also descend with little or no warning. That’s why Dudik advises preparing for an emergency whenever you venture into the winter wilds. Here’s what he and other wilderness experts suggest:

  • Always travel with a companion.
  • Listen to the weather forecast before heading out. The NOAA-NWS website offers in-depth backcountry forecasts.
  • Check the local road and trail conditions.
  • Avoid avalanche areas.
  • Leave your trip plan with a trusted friend or family member.
  • Make sure you are carrying extra water and food, first-aid supplies, flashlights, extra batteries, waterproof matches, blankets or sleeping bags, protective clothing (including undershirts, boots, hats and parkas), two compact tarps, a knife and other basic tools, a cell phone and signaling equipment such as a whistle, flare, mirror and bright-colored objects for signaling. REI has a handy checklist for winter hiking and camping.

Related: How to Prepare for a Blizzard

Steve Evans, MA, is an award-winning journalist with more than 20 years experience in daily news, investigative, health and business journalism. Among other jobs, he has served as managing editor of the Central Virginia Newspaper Group, as a senior writer for SNL Financial and as a staff writer for The Progress Index and the Richmond Times-Dispatch.