You’re taking a trip during a snowstorm when the conditions go from bad to worse. Before you know it, you’ve taken a wrong turn and you find yourself trapped in your car as a blizzard bears down. It could be hours or days before rescue arrives.

Sadly, the scenario has happened — many times — with deadly consequences. In November 2014, a 46-year-old man died in western New York when record-breaking snowfall buried him inside his car. During the Blizzard of 1978, eight motorists in New England died — five from carbon monoxide poisoning, according to the Centers for Disease Control and Prevention.

Mykel HawkeSurvival expert Mykel Hawke, a U.S. Army Special Forces Green Beret veteran and co-star of The Travel Channel series “Lost Survivors,” said the key to overcoming this scenario is planning.

“Of course, the most important thing is readiness and being ready means always thinking what if this or that happens,” says Hawke, who also starred with his wife, Ruth, on Discovery Channel’s “Man, Woman, Wild.”

Be prepared

Before the cold sets in, winterize your car and make sure it’s stocked with essentials you may need in a snowstorm, including a shovel, blankets, signal flares, sand or kitty litter, first aid kit, tools and jumper cables.

In a blizzard, it’s best to stay off the roads. But if you have no choice but to drive, you’ll want to prepare for the worst, especially if you are in a rural area. Load up the car with extra supplies such as dried foods, water, your medications, extra gas (stored properly), hand and feet warmers, warm clothes and even plastic bags for sanitation. Always tell friends or family your primary and alternate driving routes and what time you expect to get to your destination so they can help rescuers find you.

Related: 4 Key Tips for Safe Winter Driving

Make sure your cellphone is fully charged, that you have a car charger and that your gas tank is topped off.

“Just imagine what you would want for yourself if you had to spend 24 to 72 hours in your car,” says Hawke. “Then think for the whole family. Keep blankets, pillows, jackets, umbrellas, flashlights, and the usual survival kit, medical kit and survival tools you’ll need.”

When traveling, make note of where you are, the last exit numbers you saw or landmarks. That way, if you have the ability to call for help, you can give rescuers an approximate location.

Survival basics if you’re trapped

If you and your vehicle become stranded in the snow, attempt to free yourself. If you can get out of the car, dig out the wheels and use sand or kitty litter for traction. Carefully use the brake and accelerator to rock the car, but don’t strain the engine; you’ll need the car working to increase your long-term survival chances.

If trying to free yourself fails, you’ll most likely need to wait out the storm. Use your cellphone to call for help. If you reach someone, give them your current or last known location (your GPS may offer coordinates).

Related: 9 Ways Your Cellphone Can Save Your Life

The most important rule, says Hawke, is to not venture out too far away from the vehicle, especially if you are in a remote area. It’s easy to become disoriented and unable to find your way back.

Hang a brightly colored piece of cloth or a “Help” sign in your window to attract the attention of passersby. Warm your car by running it 10 minutes each hour — but first clear a large area around your exhaust pipe to reduce the risk of carbon monoxide poisoning. When running the car, turn on your interior light and use your flashers to get attention. Newspapers, magazines and even floor carpets can help insulate windows from the cold or serve as blankets if you don’t have any. Slightly open a window facing downwind when the car is running.

“The chill factor from the wind kills faster than anything,” says Hawke. “If you run the car, consider how much gas you have and how long you estimate you’ll be there… A big consideration is not using the heat during the day and saving it for night when it gets really cold.”

If you’re trapped with someone, share body heat to keep warm. It’s best to regularly move your arms and legs for exercise. Be sure to ration any food and water.

After the storm

It may take a while for the region to clean up after a major storm, which means you could remain isolated for several hours or longer. Don’t leave the car unless the opportunity for assistance is very near, or you have no other option.

If you choose to wait, provide obvious signals that you’re in distress and need rescue, says Hawke. “Try writing “SOS” or “HELP” in the snow and making an arrow pointing to you in an area folks might be more inclined to see.”

Related: 5 Emergency Apps Everyone Should Have On Their Phone

Ronald Agrella is a freelance writer and former editor of The Boston Globe’s Boston.com.