Before the first hard freeze, check ten things: battery (a free load test at most parts stores, plus clean terminals - cold cuts a lead-acid battery's cranking power roughly in half near 0degF versus 80degF while also thickening oil); tires (tread depth via the quarter test, pressure - which drops about 1 psi per 10-degree F fall, and whether winter tires make sense below about 45degF); coolant (level and freeze-point, checked with a squeeze-bulb hydrometer); wiper blades and washer fluid (summer fluid can freeze solid, so use fluid rated to -20F or colder); lights (walk around with all of them on); cabin heat and defrost; brakes (listen for squealing, feel for pedal pulsing); and oil (confirm you are current on interval, since cold oil is thicker and slower to circulate on a cold start).
In snow-belt climates, prioritize the battery load test, winter tires (or confirmed tread on all-seasons), coolant freeze protection, and winter-rated washer fluid. In mild climates, winter tires typically are not worth the cost since all-seasons stay in their working range, though battery, lights, and wiper blades still matter. This checklist covers items a factory schedule does not call out by season; a vehicle's regular mileage-based schedule (oil, brake inspection, coolant service life) is the more reliable source for exact intervals on that specific car.