Why freeze-thaw is worse than the cold
The most aggressive period for a vehicle in Vaudreuil-Dorion is not January, it is the freeze-thaw cycle that runs from late November to early March. Salt brine soaks into every seam, and the drying cycles concentrate the chloride exactly where panels meet.
That is why rust shows up first under door edges, around the rear wheel arches and on the lower tailgate. The water leaves, the salt stays behind, and the metal underneath has nowhere to hide.
What to do before the first snow
A pre-winter detail with a paint sealant or fresh ceramic top-up gives the salt something to slide off of rather than bond to.
Pair that with an interior fabric protector on carpets and floor mats, because the salt that drips off your boots dries into the very fibres that are hardest to clean later. Treating the surface before the contamination is faster, cheaper and more effective than scrubbing it out in March.
The mid-winter habit that matters most
During winter itself, the single most useful habit is a touchless rinse every ten to fourteen days, focused on the underbody and wheel wells. You do not need a full wax, you just need to keep chloride from sitting on bare metal.
Skip brush washes when possible. Cold abrasive grit on a brush is what creates the swirl marks owners try to polish out in spring, and it strips protective coatings faster than weather alone.