Well, ND is especially brutal in the winter; open prairie.
What I was thinking that even in their car, if they had some spare clothes or something, blankets and got together with their body warmth, they might have been able to survive but to her rightful credit, she didn't want to take a chance, so I guess she did the best thing.
ND can have wind chills up to 30 below, maybe even 60 below. There are odd cases where places have gotten 80 below wind chills, not the norm but it happens I understand.
Fairly ordinary winter days in ND have static air temps of between the single digits above to the mid twenties below zero. Add in wind usually ten to fifteen miles per hour.
The worst I have seen in ND was -60 (static air, unofficial, a local with a spirit thermometer) with a 40 mph wind. I found that on a military arctic operations chart and the wind chill is -146. We (I and a co-worker) were out in that for periods up to 15 minutes at a time, and had to heat the propane tank every hour or so to keep the furnace in the mobile lab going.
I have seen -54 in Riverton, WY. Thank God the wind wasn't blowing for that.
In Nevada, at altitude in desert terrain, temps down to -20 are quite possible.
People don't realize that deserts aren't just hot, but without the insulating effect of moisture can get very cold at night, especially in winter. Add altitude, and it can get really nasty.
Survival, ultimately, is a contest to retain enough hydration and calories to maintain homeostasis. Good survival food for this sort of situation is high in protein, oils, fats, and with some carbs. (Think pemmican and jerky, the original trail foods). Most trail mixes have nuts (oils/fats) and carbs, add in jerky for protein, and the only remaining problem is hydration.
In winter, you breathe out moist, warm air, but the air you inhale is cold and dry. There is a net moisture loss, unless you have something over your face which will capture the moisture and the air you inhale picks it back up on the way in. Even so, that only reduces the loss rate and helps you retain some body heat. The advantage of a beard is not that it is a moisture trap, but that it will build a layer of ice on the outside, effectively creating a dead air layer between the skin and the ice, which acts to retain heat in windy conditions. A moustache does the same, but tends to build icicles (the walrus look).
Clothing: A hat will help retain heat you would otherwise lose bareheaded. Up to 40% of the heat lost by a human is lost from the head. Hoods have the added benefit of being heated by air moving from your body to the hood area, and can be even better. Boots and gloves: practical walking boots which will keep your feet warm and dry, gloves or mittens to keep your hands from becoming damaged. Dress in layers: Inner layers should trap air, but not retain moisture, the outer layer should be windproof, but able to breathe when you move. layers in between can be added or removed depending on exertion levels, with the objective of staying warm, but not sweating. More clothing will be needed if you are at rest, less if you are exerting yourself.
With those objectives in mind, many of the materials inside an automobile can be used to insulate a human, too. Fabric from seat backs, upholstery, even the foam padding can be adapted to help you retain heat in an emergency. The car can be replaced. You can't.
The objective is to retain as much heat as possible, again without sweating (you lose heat as your sweat evaporates, and you will have to produce that heat later by burning calories). Jealously guard the warm air in your clothing, you pay in calories to produce more.
Patience is a virtue, being in a hurry can lead to rash decisions. Take your time, if you aren't injured, you want to stay that way, if you are, you need to be careful not to make matters worse.
Usually (especially in winter) staying with the vehicle is the preferred option. It is easier to spot than you are, especially in the winter in snow. Keep the windows and windshield clear of snow, when the sun comes out these will reflect light back toward searchers, but also let the sun warm the interior of the vehicle. That flash of a reflection off the glass can be a lifesaver.
If you are too far off the beaten path, you can dehydrate, starve, or become hypothermic long before help arrives. There are roads and trails that might not be traveled by any one for six months at a time. A few hours exposed can be fatal.
I knew a man who froze to death one night (-20) when his car slid off the road into a snowbank. He apparently got out to check on the vehicle and the wind blew the door shut, automatically locking him out. He was found the next day. He was too far from the nearest house to walk, and no one came by until the next day.
In this case, the lady made the right choice. How do I know it was the right choice?
It worked, they all lived.
