We will start with all important cooling system. You must make sure your belts and hoses are in good condition and the coolant is up to the task of not freezing or so dirty and contaminated that it ruins you water pump, hoses, radiator or heater core. Any leaks can become large leaks very quickly if not addressed when found. Any of these issues could leave you stranded on the side of a snowy/rainy dark night.
Second is your tires. They need to have good tread, no cracks in tread or sidewall which can leak air and cause very big issues. Tires also need to be inflated to their proper pressure. Check your door jam or owners manual for the proper tire pressure. If you tires are not inflated to the proper pressure they don’t have the best contact between the road and your vehicle which is a must in rain, snow or all driving for that mater. Winter tires are always a plus when in the high country where there is the possibility of snow or ice. Snow tires aren’t a magic pill but are considerably better in ice and snow but wear very quickly when used mostly on pavement so you must consider that.
Third issue and your four/all wheel drive system. It should be check for proper performance, noises and condition of bearings/joints and fluids. Make sure all of your drivers know how to operate the system properly because major damage can be caused by shifting at the wrong time or if certain systems are left in four wheel drive on pavement.
Fourth is your wiper/washer system. Snowy/rainy driving can reek havoc on your visibility so good wipers and full washer fluid which is deicing is a must. Also if the springs that hold your wipers tight against the front or rear window are not pulling correctly or the pivot area is corroded or rusty they will not work up to potential.
Fifth is the heating/defrosting system which as we all know gets used well in the winter. There are a lot of areas here that can cause issues. A defroster that doesn’t move the the windshield, blower that doesn’t blow enough to keep us warm and windows clear or a leaking heater core that fogs the windshield for you.
All of these things can cause a very bad day, so make sure you are confident with all of the systems or your vehicle before making that trip into wonderland!