Question: How does fog form?

Answer: Here we frequently see radiation fog; it is one of the most common forms of fog especially seen in fall and winter and is prevalent in valleys.

Radiation fog forms when the air right at the surface cools as the sun sets and the dewpoint reached the temperature. As the air cools it also becomes more stable and the air cools and stabilizes, so it causes the air to become saturated. Once the air is saturated, the fog will form. This first starts at the ground surface level and can spreads as the air further above the ground cools and stabilizes. This frequently happens in valleys since it is sheltered from the wind. Winds considered less than about 10-15 MPH are considered light to prevent the dry air and the moist air from mixing and disrupting the fog.

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