How is FG used in a METAR report?

FG (Fog) appears in the weather phenomena section of a METAR. Examples include: FG, FG VV002, BCFG. It falls under the "Obscuration" category.

What METAR codes are related to FG?

Codes related to FG (Fog) include: BR (Mist), MI (Shallow), BC (Patches), PR (Partial), FZ (Freezing). These are often seen together in METAR weather observations.

Obscuration

FG—Fog

Q: What does FG mean in a METAR?

FG stands for "Fog" in a METAR weather report. A visible aggregate of microscopic water droplets suspended at the earth's surface that reduces visibility to less than 5/8 of a statute mile. Fog is one of the most common causes of IFR conditions and flight delays. When visibility improves above 5/8 mile, the observation changes from FG to BR (mist).

METAR weather code reference for FG (Fog)

What Does FG Mean?

A visible aggregate of microscopic water droplets suspended at the earth's surface that reduces visibility to less than 5/8 of a statute mile. Fog is one of the most common causes of IFR conditions and flight delays. When visibility improves above 5/8 mile, the observation changes from FG to BR (mist).

Examples in METAR Reports

Here are common ways FG appears in real METAR observations:

FG

FG VV002

BCFG

Related Codes

These METAR codes are commonly seen alongside FG or describe related weather phenomena:

Mist

Microscopic water droplets or wet hygroscopic particles suspended in the atmosphere, reducing visibility to between 5/8 of a mile and 6 miles. The abbreviation comes from the French word 'brume.' Affectionately known among pilots as 'baby rain,' BR is one of the most frequently reported obscurations and often accompanies low ceilings and stable air.

Shallow

Indicates a weather phenomenon that extends only a short distance above the surface, generally less than 6 feet deep. Most commonly used with fog (MIFG) to describe shallow fog that obscures the runway surface but allows visibility above the fog layer. Shallow fog can make taxiing hazardous while flight visibility may be adequate.

Patches

Describes a weather phenomenon occurring in irregular patches across the observation area rather than uniformly. Most commonly seen as BCFG (patches of fog), meaning fog covers some areas of the airport but not others. Patchy conditions can create unpredictable visibility changes during taxi, takeoff, and landing.

Partial

Indicates that the weather phenomenon covers a significant portion of the airport but not all of it. PRFG (partial fog) means fog obscures part of the airport, such as one end of the runway, while other areas remain clear. This can create significant challenges for approach and landing operations.

Freezing

Indicates that liquid precipitation is freezing upon contact with surfaces at or below 0 degrees Celsius. Freezing rain (FZRA) and freezing drizzle (FZDZ) are among the most dangerous weather conditions for aircraft, causing rapid ice accumulation on wings, control surfaces, and engine inlets. Freezing fog (FZFG) deposits rime ice on exposed surfaces.

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