Having an emergency kit for your vehicle is much more important in winter. Being stuck in a remote area at below freezing temperatures can quickly become a life threatening situation. Hypothermia is the main danger to avoid.
Obviously prevention is the best way to deal with this so keep your car tuned up and ready for winter. You should prepare for the possibility of staying 72 hours in your vehicle when assembling your winter survival kit.
There are three main courses of action that could happen during a winter emergency.
1. Get the car going
This is what you want, either you get the car unstuck, refill the gas tank, jump start it, someone tows your vehicle etc. You’re drinking hot chocolate an hour later.
2. Signal for help and wait
This is not as great but could be worse. You recharge your phone. Walk a mile or two and get cell phone reception and signal for help. Or you wait for two or three days in an area without cellphone coverage, and turn on your personal locator beacon if you consider your life to be in danger. You fire up a flare and someone else brings help. You probably will drink some hot chocolate before the day is over.
This is the most challenging outcome, depending on how far help is. You’ve waited for four days, nobody knows you are missing, and nobody is searching for you. You realize that your on your own and the only way to survive is to walk for help. I’m not sure if or when you’ll drink hot chocolate.
Your vehicle’s winter survival kit should be based on preparing for those three scenarios and really encouraging the first two. Adjust your kit according to how remote or urban your commute or trip will be. You obviously don’t need a flare if you only drive in New York.
Below is how you can cover your needs for self-rescue, shelter, signaling, water, and food with a winter survival kit for your car.
How to prepare a winter survival kit for your car:
Gas: you should have a small gas container as an emergency reserve.
Jumper cables: they should be long, because snow could make it hard for the vehicles to get too close.
Windshield ice scraper and brush: where I live this is an everyday use item in winter.
Tow rope: in case another vehicle can pull you out of trouble.
Shovel: A backcountry shovel is specifically made for snow and is very compact; works much better than a folding shovel or entrenching tool.
Traction tool: Forget cat litter, if you are really stuck you will want an actual traction tool.
Tire chains: depending on how bad the snow can get in your area you might want to have tire chains or cables.
Vehicle Tool kit: You should have pliers, screwdrivers, and wrenches etc. for vehicle repairs.
Spare Tire and Jack: self explanatory
First aid kit: you should have a basic kit in case of an accident.
Cell phone charger: a usb phone charger that works out of a 12v cigarette plug.
Personal locator beacon: only meant to be used when life or limb are in danger. If you drive in a very remote area a PLB might be your only reliable way of signalling for help.
Mirror: A signalling mirror is a simple way of signalling during a bright day.
Lighter: also fulfils the need for fire, a lighter can be built to make a signalling fire and will outlast any flare.
Warm jacket: don’t throw away your old jacket, keep it in your winter survival kit.
Warm mitts: Snowmobile mitts are the warmest.
Beanie or toque: you might already wear a warm hat in winter anyway.
Warm boots: or overboots: having warm boots not only will help you keep your feet warm. They allow you to walk for help if needed. Overboots are compact and can be worn on top of your everyday shoes to make them waterproof and warm.
Thick socks: they should not fit too tight with your boots.
Sleeping bag: Having a winter sleeping bag would make your life much better if you need to stay outside for the night. A cheap synthetic sleeping bag would do the job.
Stormproof matches: they are waterproof and last longer than regular matches; they complement a lighter.
Tinder: nothing beats cotton balls dipped in petroleum jelly as an all-weather tinder for starting a fire.
Candle: having an emergency candle can help you start a fire, and have light.
Hatchet: By no means necessary, a six inch hatchet would be a compact yet effective way of cutting firewood.
Snow melting pot: an inexpensive steel pot or a can with wire bail handles would be reliable ways of melting snow for hydration. I’ve read many lists of this type mentioning carrying water bottles in their vehicles. Where I live water would only last a few hours before turning into ice.
Pack: You might need to carry extra clothes, sleeping bag on your hike. A 30-40 liter pack should suffice
Duct tape: can be used to improvise clothes and shelter
Paracord: can be used to improvise clothes and shelter
Multi-tool: having a multi-tool could help you make tinder for a fire, cut a seatbelt or improvise clothing.
Map and Compass: for navigating towards help.
Headlamp: More practical than a flashlight, a headlamp would make everything easier at night. It should last long, have extra batteries, and have a low setting, most modern headlamps chew batteries like crazy.
Food is not required for a 72 hr scenario, but it can provide an attitude boost.
High energy snacks: Macadamia nuts last a long time and can give you a small energy boost.
Bouillon cubes and hot chocolate powder: a morale boost more than anything, they help you keep hydrated in the cold.