What does BKN mean in aviation weather reports and how much of the sky is covered?

Clouds aren’t just pretty to look at. In aviation, they’re information—actionable data you read before you head out. If you’ve ever scanned a weather observation and spotted the term BKN, you might wonder what exactly that means for what you’re about to do up there. Here’s the quick, practical rundown you can lean on when you’re sorting through cloud reports in LAWRS-style observations.

What BKN really means, in plain language

BKN is short for Broken. It’s one of the standard sky-cover codes used to describe how much of the sky is hidden by clouds. When you see BKN in an observation, it means a lot of the sky is covered, but not every last patch is wrapped in cloud. Specifically, broken means roughly five-eighths to seven-eighths of the sky is cloud-covered.

To put it in context with the other common codes you’ll see:

• FEW: about 1/8 to 2/8 of the sky is covered.

• SCT (scattered): about 3/8 to 4/8 is covered.

• BKN (broken): about 5/8 to 7/8 is covered.

• OVC (overcast): all eight eighths are cloud-covered.

This eight-eighth system is the standard way meteorologists and pilots describe sky cover, so everyone’s speaking the same language even when the weather looks different at dawn, noon, and dusk.

Eight little pieces of the sky—a quick mental model

Think of the sky like a pizza cut into eight equal slices. FEW is a few missing slices; SCT is more than a few but not a full pie; BKN is most of the pizza, with some gaps here and there; OVC means the whole thing is covered. This mental image isn’t just cute—it helps you gauge what you’ll see from the cockpit or from approach control, and it guides decisions about visibility, flight level, and whether a route is practical.

Reading a cloud-cover tag in practice

In a METAR or LAWRS-style observation, BKN is paired with other clues: the cloud base (the altitude at which the clouds start), the type of clouds, visibility, and weather elements like rain or mist. Here’s how a typical line might guide you:

• BKN030 means broken clouds with a cloud base at 3,000 feet AGL (above ground level).

• If you see BKN080, the cloud deck is up around 8,000 feet, still breaking in spots but generally stacked higher.

• Add in visibility: if the visibility is good but the sky is BKN, you can still plan for VFR at certain altitudes, but you’d want to keep an eye on ceilings as you climb or descend.

Why BKN matters for flight planning and safety

The ceiling—the height of the lowest layer of clouds that covers over half the sky—is a big deal. When you’re deciding on a route, you’re balancing your needed visibility with the cloud layer’s height and the likelihood of lifting or dropping conditions along the way. BKN, especially with a low base, can lower the ceiling enough to push you into MVFR or IFR conditions. That’s not a scare tactic; it’s a practical cue to adjust altitude, speed, fuel margins, or even the departure window.

A few concrete consequences you’ll feel

• Navigation and routing: A BKN deck at a low base can limit your comfortable VFR altitudes, nudging you toward higher-altitude routes or alternate airports.

• Weather interactions: Broken clouds often bring surface-based phenomena like lower visibility in precipitation, mist, or drizzle that can creep in under the deck.

• Instrument flight rules (IFR) readiness: If ceilings are in the 1,000-foot to 3,000-foot range, you’re flirting with MVFR territory. Push the other way if you need to maintain VFR separation.

• Safety margins: Even with BKN, you can have pockets of clear air. Those gaps aren’t guaranteed; you plan for the worst while hoping for the best.

A real-world angle: reading the tape at a glance

Let me explain with a practical scenario. You’re checking a LAWRS feed before a light cross-country flight. The observation says BKN035 and visibility 6 miles, with light rain. The BKN035 means the cloud deck is mid-low at about 3,500 feet, broken across most of the sky. Visibility is decent, but the weather element (rain) and the near-3.5k ceiling suggest you might be in or near MVFR during the approach, depending on your airport’s surrounding terrain and your cruising altitude. You’d plan your leg burns and alternates with that ceiling in mind. If you’re staying in the pattern for a few touch-and-goes, you’ll track whether the deck lifts or drops and adjust your practice session accordingly.

Why the term matters in the LAWRS ecosystem

The Limited Aviation Weather Reporting System (LAWRS) isn’t just about raw numbers; it’s about translating those numbers into clear, actionable flight decisions. The sky-cover designation—FEW, SCT, BKN, OVC—gives you a quick, standardized read on how “cloudy” it is up there. Pilots, dispatchers, and air traffic controllers all rely on that shorthand to keep a flight moving safely and efficiently, even when the weather is shifting by the minute.

Pairing BKN with other clues for better decisions

Here are a few quick checks you can run in your head when you see BKN on a report:

• Check the base: Is the base high enough to allow the aircraft’s altitude for your planned legs? If not, think about a different altitude or a different routing.

• Look for precipitation indicators: Rain, snow, or mist near a BKN layer can worsen visibility and floor the ceilings even more.

• Gauge the horizon: If you’re near the airport, a BKN deck can mean the “ceiling” may bounce around as you transition from takeoff to climb-out, then into cruise. Plan your climbs and descents with those potential changes in mind.

• Consider alternates: If the layer is stubborn and forecasts show it staying put, having a viable alternate airport with a higher ceiling can be a lifesaver.

A few reader-friendly takeaways

• BKN equals 5/8 to 7/8 cloud cover. It’s not complete overcast, but it’s heavy enough to affect visibility and ceiling planning.

• The cloud base is your next crucial clue. A low base with BKN can constrict VFR operations more than a high-base BKN deck.

• It’s all about the digits plus the weather mix. Clouds are a big part of the whole weather story, but rain, fog, and wind all color how you’ll actually fly through that sky.

Practical tips for staying sharp with cloud-coverage terms

• Keep a simple cheat sheet in your notebook or on your tablet: FEW 1-2/8, SCT 3-4/8, BKN 5-7/8, OVC 8/8. Then pair it with the base height numbers you commonly see (for example, BKN030, BKN050).

• When you see BKN, scan for the base altitude first, then look at visibility and weather. The base is the ceiling you’ll most likely be maneuvering around.

• Use a mental model of the sky as a layered map. Even if you can’t see the clouds from the ground, the data tells you where the “layers” sit relative to your planned flight level.

• Don’t ignore the human factor. Controllers may use the same codes, but their guidance will hinge on your intended departure time, route, and current weather picture. Stay in touch and keep your plan flexible.

A few practical tools you’ll find handy

• METARs and TAFs: They’re the bread and butter of aviation weather. Look for the sky-cover descriptor and cloud-base height to build your picture for the flight.

• LAWRS feeds and other standardized observations: They give quick, reliable snapshots of cloud cover alongside visibility and precipitation.

• Aviation charts and flight-planning apps: Many of these tools now annotate cloud bases and coverage in a way that’s easy to digest, helping you translate BKN into a safe plan without getting lost in the numbers.

A final reflection: knowledge that travels with you

Understanding BKN isn’t about memorizing a quiz answer; it’s about building a reliable instinct for what the sky is telling you. When you know that BKN means five-eighths to seven-eighths of the sky is cloud-covered, you’re equipped to anticipate ceilings, plan safe altitudes, and decide whether you can stay VFR or need to switch to instruments. It’s a small piece, but it anchors your decision-making in real-world flying.

If you’re curious, there are plenty of real-world scenarios where this knowledge matters—from a quick hop between nearby fields on a hazy morning to a longer cross-country where a stubborn deck can shape an entire day’s plan. The sky is full of clues, and cloud-cover terms like BKN are the shorthand that helps you read them quickly, accurately, and calmly.

In the end, the goal isn’t to chase the perfect forecast but to fly with confidence, armed with a clear picture of what the clouds are doing and how that affects every mile of your journey. With BKN in your toolkit, you’ve got one more reliable indicator to lean on, one more piece of the weather puzzle that makes air travel safer and more predictable. And that’s the kind of clarity every pilot loves when the weather starts to look a little unpredictable.

Short recap, just for practical recall

• BKN = Broken = 5/8 to 7/8 sky cover.

• Sky is divided into eight parts for a consistent read.

• Cloud-base height with BKN tells you a lot about ceilings and potential VFR/IFR shifts.

• Use BKN alongside visibility, precipitation, and cloud type to guide your flight plan.

• Keep a quick-reference cheat sheet handy and let the data guide your decisions, not guesswork.

If you’d like, I can tailor a quick, reference-style companion sheet for BKN and the other sky-cover terms so you have a ready-to-use guide at a glance during your next flight briefing.