Mount Southington is close enough to most of the town that a lot of local cars make the same trip a dozen times a winter — up to the hill, a few hours there, then home with everything still wet.
The damage is not the snow. It is what comes off the boots with it.
Car-park grit is not garden mud
A ski area car park gets sanded and treated heavily, because it has to be. Boots cross it, pick up sand, salt and fine grit, and carry all three into the footwell, where they sit for the drive home with the heater running.
Two things then happen at once. Meltwater carries the grit down into the carpet backing instead of leaving it on top, and the heater dries the surface while the underlay stays wet. That combination is why a ski car develops its particular smell by February.
Plain mud dries and can largely be brushed and vacuumed out. Treated grit dissolves, migrates, and re-crystallises in the fibre. A vacuum lifts very little of it.
Why a season is worse than a trip
Almost nobody cleans up after a single ski day, which is reasonable. The problem is that each trip lands on carpet that never fully dried from the last one.
By March you have several months of chloride in the backing, a footwell that is permanently slightly damp, and often a white tidemark along the carpet edge where salt has wicked up and dried. The tidemark is the visible clue that there is much more you cannot see.
The same applies to the boot if that is where skis travel, and it is worse if they go in wet against a folded rear seat.
What actually removes it
Hot-water extraction. Heated solution goes into the carpet under pressure, the bound salt and grit dissolve back into it, and it is pulled straight out again by vacuum. It is the only method that removes material dissolved into the fibre rather than sitting on top of it, and it is included in our interior detail at $175 and in a full detail at $275.
Rubber mats help a great deal and most Southington cars should be on them from November. They do not solve it alone — grit tracks past the mat edge onto the carpet under the seat, which is the part nobody checks.
When to book it
End of season, once the hill closes, rather than mid-winter. Cleaning in January means doing it again in March.
The exception is a car that has started to smell. That means the damp layer has been damp long enough to grow something, and it is worth dealing with now rather than in April.