Window frost is sometimes called fern frost due to it’s beautiful fern-like pattern.
But how it is formed, and why are these ferns present on your windshield only sometimes?
On cold, often clear nights, the glass on your vehicle cools as it loses heat to the air around it.
When it cools below the temperature of the air, the moisture in the air begins to “deposit” onto nuclei on the glass. Deposition is when water transforms from a gas phase directly to a solid phase, without becoming a liquid.
These nuclei can be anything from dirt to dust to minute imperfections in the glass.
Once a nucleation point is created, the crystal begins to grow.
It grows just like a snowflake, in a fractal pattern, meaning in expanding symmetry but in two dimensions creating the fern-like pattern.
The shape or design of these ferns are influence by the shape and position of the nuclei on the windshield.
In essence a perfectly smooth and clean window will likely have fewer patterns.
WATCH: BC Evening Weather Forecast: Jan 23
However, this is no excuse to keep your windshield dirty, as the weather conditions need to be just right for these types of crystals to form.
Have a photo of window frost you want to share? Send it to us at email@example.com.