Winter has a way of turning your car into a small moisture trap.

Cold mornings often bring foggy windows, damp floor mats, stubborn frost, and condensation that seems to appear out of nowhere. If your vehicle stays outside overnight, you may notice that the interior becomes surprisingly humid—even when there are no visible signs of a leak.

This is where a simple household ingredient comes in: salt.

You may have come across the viral tip of leaving a glass or small bowl of salt inside your car overnight. While it sounds almost too easy to work, there is some science behind the idea. Still, it’s important to understand what this simple trick can realistically accomplish.

Why Put Salt in Your Car?

Salt can attract moisture from its surroundings, although how effective it is depends on factors such as humidity, the type of salt, and the amount being used.

The principle is straightforward:

Moisture in the air → salt draws in some of that moisture → humidity inside the car may be reduced.

Lowering excess moisture can help when your vehicle frequently develops condensation on the windows or has a generally damp interior.

That said, a small glass of ordinary table salt isn’t going to completely dry out a waterlogged car overnight. It’s better viewed as a simple moisture-control trick rather than a solution for serious dampness.

How Does the Salt Trick Work?

If you’d like to try it, choose a small, sturdy container that is unlikely to tip over.

Fill it with some dry salt and place it in a secure area inside your parked vehicle. Leave it there overnight and check it the next morning.

As the salt interacts with moisture in the air, it may become damp or start forming small clumps. This can be an indication that it has taken on some moisture from the surrounding environment.

A quick safety reminder: Never leave an unsecured or open container where it could spill, slide beneath the pedals, or come into contact with electrical components. Keeping it stable and out of the way is essential.