Those little tea candles can keep the interior up above freezing.

I have a gallon jug of water and some granola bars

Year round.

... during the snow months

plus I have a windup flashlight/radio in the glove box.

Blanket (old army wool)
travel pillow
water
granola/energy bars

Plus, I assume I will have my cell phone with me.

He would take old cans, usually the ones from some sort of canned meat that were wider than they were taller, and coil cardboard into it tightly then cover with wax. Made a nice little self contained fire that lasted hours (we actually used one once in the car one winter, worked great and kept us warm).

Food, water bottle, flares, blanket, etc can all fit nice into a back pack one can leave in the trunk or back seat.

And as mentioned...flares, candles, blankets, warm clothing...

I have an 'emergency' kit that contains booster cables, tow strap, flares, first aid kit, reflective blankets (those things that look like foil), reflective tape, multi-purpose knife (with pliers, screwdrivers, scissors etc)

I also have a small camp stove w/pot that runs with tea light candles in order to melt snow for water. I keep a box of granola bars too. Oh, and a couple of water bottles. An extra hat, mitts, fleece blankets, a lighter, and wind & waterproof matches, paper towels


It is actually a somewhat regular occurrence (well, once a year or so) where I live (Canadian Prairies) where people get stranded on highways because of blizzards so that's why I carry all of that stuff. If I'm going on an extended trip, I add more food and blankets. And I check the weather before I go, and if there's a snowfall warning or blizzard I don't go.

ETA: What I need to add to my kit: flashlight (cranking, no batteries b/c batteries freeze), hatchet (in case we need to build a fire if we are stranded in the boonies), kitty litter (traction on ice) and hot packs to warm hands and feet.

a few of those cheap single-use hand warmer packs

(or, if you can find them, re-useable hand warmer packs http://www.amazon.com/Toysmith-Sock-Monkey-Warmers-2-Pack/dp/B009Z1L2C0/ref=pd_sim_sg_13 )

solar/wind-up weather radio & combined cell phone charger/'flashlight, gallon water, granola or other "meal" bars. jumper cables, fix-a flat or similar...

The coffee can may be saving grace

I spent 12 hours stuck in the car coming back from skiing--when roads closed--too far from an exit... That snow plow was one welcome sight.

But, when the weather is dangerously cold, every driver should be dressed in a way that will allow him or her to be outside of the car, no matter where they go. If you're driving in or near a major city, help will arrive quickly, but if you're on a longer distance trip, it may not, so you should have a winter survival kit in your car where it can be easily accessed.

The most important thing in that kit is a charged cell phone. Calling 911 will bring help. Beyond that, here's a link to a decent list of other things worth having with you, in case you're stranded on the road:

http://www.weather.com/life/safety/autosafety/article/winter-survival-kit_2011-10-30

Then I could answer.