January breakdowns look like bad luck and are almost never random. Cold reduces a battery's available current at exactly the moment the engine is hardest to turn over, which is why a marginal battery fails on the first genuinely cold morning rather than gradually.
Battery, tires, fluids
A battery over about four years old is on borrowed time and can be tested for free in ten minutes. Tire pressure drops roughly a pound for every ten degrees, so a tire set in September is measurably low in January — and tread depth matters more in the wet and cold than any other condition. Washer fluid needs to be the winter mix, because water and summer fluid both freeze in the reservoir and in the lines.
And keep something in the trunk
A blanket, a flashlight, a phone charger, and a scraper. This is not preparedness theater — the realistic winter emergency is not a crash, it is sitting stationary for two hours somewhere cold while traffic clears.