Frost is a layer of ice that forms on solid surfaces when water vapor in the air turns solid:

 Frost is a layer of ice that forms on solid surfaces when water vapor in the air turns solid: 

How it forms

Frost forms when the temperature drops below freezing and the air is saturated with moisture. The water vapor in the air turns directly into ice crystals without becoming a liquid. This process is similar to dew formation, but it happens below freezing.

Where it forms

Frost often forms on objects like plants, cars, and windows that are exposed to the cold air. Areas with a lot of fog are more likely to have heavy frosts.

Types of frost

Depositional frost, also known as hoar frost or white frost, forms when the dewpoint is below freezing. It creates a pattern of ice crystals that can look like tree branches. If the frost is thick enough, it can look like a light snowfall.

Frozen dew

Sometimes the freezing temperature is reached after dew has already formed, which creates frozen dew. However, it's usually difficult to tell the difference because the crystals usually start forming at the same time the freezing starts.