Fog

Cloud consisting of numerous minute water droplets and based at the surface; droplets are small enough to be suspended in the earth’s atmosphere indefinitely. Unlike drizzle, it does not fall to the surface. Fog differs from a cloud only in that a cloud is not based at the surface, and is distinguished from haze by its wetness and gray color.

Source: Pilot's Handbook of Aeronautical Knowledge (definition from the FAA-H-8083-25B, 2016; current: FAA-H-8083-25C, 2023, with the October 2025 addendum).

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Glossary last updated 2024-07-25.

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