What does FG stand for in aviation weather reports, and why fog matters for pilots.

Fog, plain and simple—and yet it holds a lot of weight in the world of aviation weather. If you’re looking at weather observations, the little code FG is saying something very direct: fog is present. It’s a compact label, but it signals pilots, controllers, and planners to expect reduced visibility and to adjust plans accordingly. Let’s unwind what FG really means, how it’s used, and why it matters in the broader tapestry of weather reporting.

What FG really stands for

Here’s the thing: FG is the official shorthand for fog in meteorological and aviation weather reporting. Fog is a cloud that forms at or near the surface, made of water droplets suspended in the air. When fog is around, visibility can drop quickly, which has a big impact on takeoffs, landings, and everything in between. That’s why you’ll see FG pop up in the weather observations at airports and on weather graphics that pilots and dispatchers rely on.

A quick note on the fog family

People sometimes mix up fog with related conditions, so a quick map helps:

• FG = Fog. You’re seeing a fog layer at ground level that reduces visibility.

• FZFG = Freezing fog. The droplets are cold enough to freeze on contact, which can coat surfaces with ice. That’s a separate category, and it’s denoted with FZ or FZFG in many reports.

• BR = Mist. This is lighter than fog, with better visibility than FG but still reduces the view outdoors.

• Other terms like drizzle, haze, or clouds forming at the surface can crop up, but FG sticks to “fog” as the standard label.

Fog versus freezing fog: why the distinction matters

You might wonder why the wording matters. It’s not just trivia. The difference changes what pilots expect on contact with runways and taxiways. Freezing fog creates icy surfaces on contact, which can be slippery right away. Freezing fog often shows up as FZFG or a similar tag, signaling a different set of precautions than plain FG. On a calm morning, FG might wash out the horizon and scrub a smooth landing, while FZFG makes ice the real enemy.

So, FG is your signal that visibility is limited due to a fog layer at ground level. Freezing fog adds a layer of surface icing risk. Mist, or BR, is another warning flag—visibility is reduced, but not as aggressively as with FG. The labels are small, but they carry big consequences for flight operations and safety.

Why this matters in practice (even if you’re just learning)

For anyone learning the ins and outs of aviation weather, FG isn’t just trivia. It’s a practical cue that helps you read conditions quickly and translate them into actions. In a busy airfield, controllers coordinate with pilots based on visibility estimates. If FG is present, you might see lower approach minima, altered hold patterns, or changes to departure priorities. The codes keep communication precise and fast, which is exactly what a high-stakes environment requires.

A look at how FG appears in weather reports

A typical weather observation for a bustling airport might look something like this in shorthand:

METAR KXYZ 041653Z 17012KT 2SM FG BR OVC003 12/11 A2992

Let’s unpack that a bit:

• 2SM FG means visibility is two statute miles with fog on the scene.

• FG is the key flag here, signaling that the reduced visibility is due to fog, not rain, snow, or a broken cloud layer.

If you instead saw FZFG, that would tell you the fog is freezing on contact, adding surface icing concerns to the visibility issue.

Understanding how FG sits with other weather pieces helps you picture the whole picture: cloud cover, temperature, wind, and the all-important visibility. Fog doesn’t live in isolation; it intersects with cloud layers, precipitation, and land features. A coastal airport, for example, can wake up to fog that clings to runways after a cool night and a damp air mass. In landlocked spots, fog might be more patchy, playing hide-and-seek with the heads of approach paths.

Reading the reports with clarity

If you’re studying or simply trying to get better at interpreting LAWRS-style weather notes, here are a few practical habits:

• Scan for visibility first, and take FG as the primary signal for restricted visibility at the surface.

• Check the accompanying cloud cover. A thick overcast layer with FG can give you a sense of how far the fog might drop as the day warms.

• Look for the presence of BR (mist) alongside FG. If BR shows up, visibility is reduced but the air isn’t as dense as with FG.

• Note any remarks about runway visual range (RVR). Even when FG is present, RVR readings give you a ground truth under specific runway paths.

A little mental model helps: think of the sky as a stage and FG as a curtain that lowers the view to the horizon. The tighter the curtain, the less you can see, and the more you rely on instruments and procedures. That mental image can keep you anchored when reports stack up and the weather shifts.

Common questions pilots and planners juggle

• Does FG always mean total failure to see anything? Not at all. Fog reduces visibility, sometimes to a few hundred meters or more, but some sight lines remain. The exact numbers vary with conditions, but the key thing is: visibility is significantly degraded.

• Can FG be present with clear skies above? Absolutely. Fog sits at the surface; you can have a fog layer with clear or partly cloudy skies above.

• How does FG interact with pilot decision-making? It pushes pilots toward instrument flight rules (IFR) rather than visual flight rules (VFR) and can affect takeoff and landing minima. Controllers factor that into sequencing and spacing.

A few study-friendly tips

• Build quick flashcards that pair FG with its meaning, plus a separate card for FZFG and BR to prevent mix-ups.

• Practice with real METAR snippets. The more you see FG in context, the easier it becomes to recognize quickly.

• Use official sources as a reference: aviation weather centers and national meteorological services publish the codes and their meanings. They’re reliable, concise, and designed for fast interpretation in the field.

• Pair reading with a mental clock: fog often forms in the early morning and can lift by late morning as heating air improves mixing. That sense of timing helps with forecasting and planning.

Digressions that still stay on topic

A quick thought about how weather reporting has evolved: observers used to rely on human eyes almost exclusively, with hand-drawn charts and a lot of interpretation. Today, automated stations and sensors join the human observer to give a richer, quicker read on weather. Yet the codes—FG, BR, FZFG—remain the language that ties all those data streams together. It’s a neat reminder that while the tools change, the need for clear, shared meaning stays constant.

Putting it all together

So, what does FG signify in weather observations? Fog—plain and unmistakable. It’s the shorthand that tells pilots and controllers: visibility is reduced at the surface due to a fog layer. Freezing fog has its own badge, FZFG, signaling ice risk on contact. Mist has its own label, BR, indicating a different level of visibility restriction. Understanding these distinctions isn’t just about memorizing letters; it’s about translating a compact code into real-world actions that keep flights safe and flights on track.

If you’re curious about the real-world heartbeat of reporting systems, consider how observers, automated stations, and air traffic control work together. The goal is simple: get pilots the right information, at the right time, in a form that’s fast to read and hard to misinterpret. FG is a small but powerful piece of that puzzle.

And one last thought to anchor the idea: the next time you see FG on a weather update, picture the fog as a thin, ground-hugging veil over the airport. It’s not just a weather quirk; it’s a signal to slow down, check the instruments, and plan the next move with care. That mixture of precision and practicality—that’s what aviation weather is all about, every day, in every report.

If you want to explore this further, you can glance at example METARs from major airports and watch how FG and its kin appear and disappear as the day unfolds. The more you see, the more natural it feels to read the weather like a fluent speaker of the aviation weather language. And when you get it, you’ll notice confidence rise—because you’re not just reading codes, you’re interpreting what they mean for safety, schedules, and the art of flight.