Winter breakdowns are dangerous in ways summer breakdowns are not. A dead battery at 75°F is an inconvenience. A dead battery at -5°F is a medical risk. Every vehicle driven through winter should carry a kit that makes a 2-hour wait for a tow survivable.
Essential items: a thermal blanket (the small silver Mylar ones pack to the size of a paperback and can save your life), a full-size fleece blanket, a winter hat and gloves stored in the vehicle year-round, a flashlight with fresh batteries (or a hand-crank unit), a portable phone charger, and bottled water.
Power safety: a lithium jump pack ($80-$150) lets you self-resolve most dead-battery scenarios without waiting for a tow. Keep it charged — check it monthly. These same packs can also charge a phone if your car's 12V system is dead.
Traction: small bag of sand or cat litter can free a vehicle stuck on ice or compacted snow. A folding shovel gets you out of most plow-berm situations without a tow.
Visibility: reflective triangles, road flares, or rechargeable LED warning lights. If you break down on a shoulder in poor winter visibility, you need drivers to see you from several hundred feet away.
Phone: saved contacts for your preferred tow service (Toll Trucks Near Me: (888) 831-3001), your auto insurance roadside line, and your auto-club membership number. A frozen phone screen is harder to navigate than warm hands expect.
Pre-trip: check fuel (avoid driving on fumes in winter), check tire pressure (cold air drops pressure), check washer fluid (sub-zero formulation only), and know the route. Tell someone where you're going and when you expect to arrive.