Along with Owen'* suggestion of blankets, I'm going to add bottles of fresh water. Keep them in the back seat so if they do freeze, they may thaw out by the time you need them. A flashing LED beacon light, flashlight, granola bars/energy bars should you become stranded in a ditch or the highway shuts down. An extra mobile phone charger that you keep solely in the car. A portable weather radio. Heavy hunting socks and maybe an extra pair of good boots.

putting water in is a good way to get a wet trunk, freezing water expands to break the container and thaws to ruin your trunk

Did you ever notice the newer water bottles are expandable?

yep, but i doubt it would go well im not trying it

Ya Winter...We get it in Dec- Mar especially in the mountains and down to -40 at elevation.
My trunk is always loaded with gear,spare clothes/ blanket, water, tools, candles, waterproof matches, first aid etc etc...
I add to list 24 gas line antifreeze bottles with water remover, if going super subzero temps, and keep it in fuel at fill ups. I also have cardboard & plastic to cover grille with me for rad to help keep things warm in cabin. Radial chains are a necessary investment too if it gets real nasty & deep. Studs are allowed here as well and a good choice for icy mountain passes. Even though I travel mainly with the Pk Ave in 70% of the year, when it comes to our mountains and winter, I switch to the 4x4 with Silent Armor Tires and have a set of chains for it. If you want to see our conditions in winter watch the new show on Discovery TV on Tues night Called Highway Thru Hell. Ya stay away from the big rigs on the summit of Coquihalla Hwy going North. Talk about white knuckle driving and only for the prepared and experienced with proper vehicles.
TV Show Link: http://www.discoverychannel.ca/Showpage.aspx?sid=45238
I use Tridon winter wipe Blades for the winter only then store them. I also use -50 washer fluid with prestone winter booster.
Google Image Result for http://i1-store.walmart.ca/images/WMTCNPE/409/009/409009_Enlarged_1.jpeg

Always let someone know where you're going.

It'll be my first winter with the truck, but I'm over prepared now, just a matter of putting some heavier extra clothes in.

I use Black Magic tire spray on seals. Spray on towel first, then wipe down. Its mostly silicone, which repels water, and cooking grease just makes stuff smell weird after awhile.
Don't forget to spray your tires! The UV light drys out the sidewalls.

I don't rely on jumper cables. No way. Not even the pros will use them. Too much risk of an arc frying something important. Get a good jumper pack with an on/off switch and a charge indication gauge. If no one else is around, who are you going to get a jump off of? Always assume you wont see another car if things happen.
Get AAA Gold. Worth it! Towing for 100 miles, gas, jump start, much more. Had AAA for many years, and completely worth it. One tow will cover the membership fee and then some.
If you have AAA and an android phone (not sure if theres an I-equal), download AAA Roadside Assistance. You press a few buttons, it takes your GPS signal and sends it to dispatch. Sends you a text back with an ETA. It stores your card no., and your membership info. Much simpler and less nerve-wrecking than trying to call them after an accident, or getting stuck. You don't have to figure out where you are, find your account number, even your vehicle info is stored (if you want it to be).

Look at your insurance policy to see what is covered. Change as needed. You may want to put full coverage on, just for the winter, just in case if you don't have it already.

Download radar apps and just be aware of the weather. So many people are caught off guard because they never took the time to check up on weather and road conditions before they head out. Situational awareness!

Always leave earlier than you think you need to. If you can, travel when traffic is lighter (not rush hour). You can concentrate on your own driving more, and other peoples driving less. But always be aware of "the other guy".

Hot hands/feet chemical packs. Always have some. Cheap, and they work.
Flares. Have some. Too many accidents caused by people who can't see you in time.
Mobile NOAA weather radio. Cheap insurance. As a storm spotter, I can tell you they can literally save your life. They make some good combo radios that work off solar, battery, or hand crank.
Flashlights and batteries. Can never have enough.
Get some water jugs (3L bottles), get rid of the top 1/4, and add about a shots worth of vodka. Been there, done that, it works. If in doubt, put them in a good insulated cooler. The same thing that keeps your drinks cold in summer can keep your water from freezing in winter.

If you are really remote, pick up a battery powered HT (Handy Talkie) 2M radio. I've seen some go for $60. Small mag mount antenna. Technically not supposed to do this without a license, but if you are desperate in emergency, and out of cell range, they can also save your life. Someone might just pick up that signal. Not enough people listen to CB anymore, so those portable ones really aren't worth it.

Common sense. You can never have enough.
Follow Skywarn'* acronym: ACES
A=Awareness. Watch the weather, listen to the radio, check the forecasts.
C=Communication. Tell someone where you're going. Call ahead to work to see if there is any trouble in that area, or someone there may suggest an alternate route.
E=Escape Routes. You might think you can make it, but the roads may turn bad in no time. Plan alternate routes, and carry a real map (not a GPS, but a real up to date area map. And learn to read it!)
*=Shelter. If you are stuck, and may be awhile before help comes, have a plan. Sleeping bag for warmth. Hot packs, gloves, wear layers. Have a change of clothes if you get wet. Be prepared with some simple food, granola bars, trail mix, etc. Burning calories keeps you warm. Protein is best. If you have a large vehicle (van, SUV) have tape and a large blanket. If you divide up the space in the vehicle to keep the heat around where you are, your body heat is contained to a smaller part of your vehicle. Make sure to have some signaling device (strobe light, bright colored flag/cloth, road flares) in case you hear something.

Can you tell I've lived and traveled in upstate NY for all my life?

I have lots more, but the post is already going insane long. But I have a backpack for emergencies, and being a trained medic, a large first aid kit is a must. There isn't enough site bandwidth to go into those packs.

All great ideas.

The number one thing for winter in my vehicles are qty 2 washer fluid in the trunk. I can deal with a flat, not starting etc. But there is nothing I can do when the snow is melting and there is dirty spray all over the road. The only fix is washer fluid.

When I need washer fluid so does everyone else, often resulting in the stores being out of stock. I buy a bunch when it is on sale in the fall and always keep two bottles in the trunk. One for me and one for a friend....

For me I do a lot of the basics mentioned already, check tire pressure an adjust, all fluid levels are checked, and winter washer fluid is used, wipers are checked/replaced if necessary.
I am not as prepared as I'd like to be as far as what I carry, I just have a LED flash light, and one that is magnetic that I can stick under the hood if I need to see to work on something, I always carry water with me but I do not leave it in the car, I keep oil, brake fluid, transmission fluid, and pre-mixed antifreeze, but those are things I like to keep in the car at all times, not just in the Winter.
I keep my jump box charged and in the car.
And if weather is bad, and I have to drive far, then I'll take some granola bars, trail mix, or nuts wit me, just in case I get stranded for a while..


For my Winter safety list I have a few items on Amazon that I plan to get when money allows.

i need a tonneau cover..

What does this have to do with the topic at hand?