You can purchase a pre-made car weather safety kit or build your own. Even if you decide to purchase a kit, be sure you are familiar with the contents! Learn to use all of the supplies in the kit! When you are freezing cold, and possibly wet, you will NOT want to look at the directions on a bottle.
> Get blankets or sleeping bags such as a space blanket
> Flashlight with extra batteries. There are even self charging flashlights with cell phone chargers.
> You absolutely need an auto first aid kit.
> A knife and some high-calorie, non-perishable food.
> A large empty can and plastic cover with tissues and paper towels for sanitary purposes plus a smaller can and water-proof matches to melt snow for drinking water.
> Sack of sand (or cat litter) for tire traction and a shovel.
> An auto emergency tool kit. Kits should include tow ropes, windshield scrapers, jumper (booster) cables, and a first-aid kit.
> A compass and road maps.
> You may also want to bring along a winter safety handbook.
> Extra clothing to keep dry for all of the vehicle occupants.
> Keep your gas tank near full to avoid ice in the tank and fuel lines.
> Try not to travel alone, especially in unfamiliar places.
> Let someone know your timetable and primary and alternate routes.
> Fully check and winterize your vehicle well before the winter season begins. Be sure the tread on your tires is good enough to last throughout the entire season. Install chains on the tires if necessary.
> One final note about automobile safety kits…No kit can fully prepare you for a winter driving season and all of the contingencies that could arise as a result of a sudden change in weather patterns. Because preparation is the key, make sure that you think about the individuals you will be protecting in your car or truck. Each may have their own needs. It is a better idea to pack extra of the supplies needed than to be stranded without the proper equipment.
Information from about.com