What Does FG Mean in a METAR?
FG means fog. It stands for FoG.
FG in a real report
FG
That reads as fog (visibility below 5/8 SM).
What it changes for you
Fog is the most common cause of a diversion in otherwise calm weather. It forms fast and sits below approach minimums. It often covers one field while the next one along is clear.
Watch for the forms that change the picture:
FZFGis freezing fog. Below zero, the droplets freeze on contactMIFGis shallow fog, less than 6 feet deep. The runway can be obscured while the tower sees the sky perfectly wellBCFGis patches of fog, so conditions vary along the runwayPRFGis partial fog, covering part of the field only
What to read next to it
Fog with VV002 rather than a cloud layer means the sky is obscured. The 200
feet is a vertical visibility, not a ceiling. That matters on approach: you
cannot see through an obscuration the way you can see through a gap.
Related codes
Decode a report containing this code
Paste a METAR, TAF, PIREP or SIGMET into the WxDecoder decoder. Every group comes back in plain English. The raw code sits beside it, so you can check the decode rather than trust it.
Frequently asked questions
What visibility counts as fog in a METAR?
Less than 5/8 of a statute mile. At or above that the same phenomenon is reported as BR for mist. Fog is water droplets suspended at the surface, so it is a visibility restriction rather than a cloud layer.
What is the difference between FG and FZFG?
FZFG is freezing fog: the droplets are supercooled and freeze on contact with an aircraft or the runway. It occurs at temperatures below zero and is the version that deposits ice on your airframe while you are still on the ground.