FEW, SCT, BKN, OVC: Which Layers Are a Ceiling

The sky-condition section of a METAR lists each cloud layer with a three-letter coverage code and a height, low to high, like FEW020 BKN045 OVC100. The trap is that not every layer matters equally for an instrument approach. Only BKN and OVC layers, or vertical visibility, define a ceiling, so FEW and SCT layers never count toward IFR minimums. Once you know how coverage and height are encoded, the lowest broken or overcast layer jumps out, and wxdecoder labels it for you.

This guide covers the four coverage codes, how the heights are written, the rule for finding the ceiling, the convective cloud types, and the clear-sky variants. It is part of the METAR field guide; for how the ceiling then drives the go/no-go picture, see VFR, MVFR, IFR, LIFR.

Coverage in oktas

Cloud coverage is reported in oktas, eighths of the sky dome covered by cloud at that layer. The observer (or the automated station's algorithm) buckets the coverage into one of four codes:

The codes are cumulative: each reported layer describes the total cloud amount at and below that height, which is why coverage tends to increase as you read up the list. A layer that covers half the sky or more, BKN or OVC, is solid enough to form an effective floor on the visible sky. FEW and SCT layers let enough blue through that they are never treated as a ceiling.

Height is in hundreds of feet AGL

After the coverage code comes a three-digit height in hundreds of feet above ground level (AGL). Multiply by 100 to get feet:

• BKN014 is a broken layer at 1,400 feet AGL.
• OVC008 is overcast at 800 feet AGL.
• SCT250 is scattered cloud at 25,000 feet AGL.

The key word is AGL, not MSL. The height is measured from the airport surface, so the same physical cloud base reads as a different number at a sea-level field than at a high-elevation one. Because the value is rounded to hundreds of feet, OVC009 and OVC010 both describe a base near 900 to 1,000 feet, which can be the difference between two flight categories when the base is hovering at a threshold.

Layers are listed low to high

A METAR reports cloud layers in ascending order, lowest base first:

FEW020 SCT045 BKN080 OVC120

Reading left to right, that is a few at 2,000, scattered at 4,500, broken at 8,000, and overcast at 12,000 feet AGL. Because they are sorted, the first BKN or OVC you reach scanning left to right is the ceiling. Everything to the left of it is FEW or SCT and does not change the answer.

The ceiling is the lowest BKN, OVC, or VV layer

Here is the rule stated plainly. The ceiling is the height of the lowest layer reported as BKN, OVC, or a vertical visibility (VV) group. FEW and SCT layers, however low they sit, are not ceilings.

Vertical visibility is the special case. When the sky is obscured (heavy fog, snow, or precipitation) and no distinct cloud base can be measured, the station reports VV### instead of a coverage code, for example VV004 for a vertical visibility of 400 feet. That value acts as an indefinite ceiling. The full mechanics are in VV001 and indefinite ceilings explained.

Worth remembering: the ceiling is only half of the flight-category calculation. The prevailing visibility is the other half, and the worse of the two wins. A field can have a high ceiling and still be IFR on visibility alone.

Worked example

Take this sky condition and find the ceiling:

FEW008 SCT015 BKN025 OVC060

The ceiling is 2,500 feet, the height of BKN025. The lower FEW and SCT layers are real cloud and worth noting on an approach, but they do not set the ceiling. The overcast at 6,000 is above the ceiling, so it does not change it either.

CB and TCU: the only named cloud types

A standard METAR does not describe cloud shape, with two exceptions appended directly to a layer group:

• CB marks a cumulonimbus, the thunderstorm cloud.
• TCU marks towering cumulus, a tall building cumulus that can grow into a CB.

So BKN040CB is a broken layer at 4,000 feet made of cumulonimbus, a direct flag for convective weather: turbulence, hail, lightning, and shifting winds in the vicinity. When you see CB or TCU, the layer is doing double duty, telling you both the ceiling and a hazard. Pair it with the present-weather group to read thunderstorm and hail codes like +TSGR.

Clear-sky variants: SKC, CLR, NCD, NSC

When there is no cloud to report, you get one of a few codes in place of any layer group:

• SKC (sky clear) is the human-observer code for no cloud at all.
• CLR is the automated-station code for no cloud detected below 12,000 feet, the sensor's reporting limit.
• NCD (nil cloud detected) is the automated equivalent used in many ICAO reports.
• NSC (nil significant cloud) means no cloud below 5,000 feet and no CB or TCU, used when conditions are not fully clear but nothing operationally significant is present.

None of these set a ceiling, because none of them is a BKN, OVC, or VV layer. A report of CLR simply means the ceiling is unlimited as far as the equipment can see.

Find the ceiling in any report

The procedure never changes: read the layers low to high, skip every FEW and SCT, and the first BKN, OVC, or VV group you hit is the ceiling, in hundreds of feet AGL. Watch for CB and TCU tags that turn a routine layer into a convective warning. To have it done for you, paste a raw observation, such as the latest at KDFW, into wxdecoder and every layer is decoded with its height and the ceiling called out. Then read the flight categories to see how that ceiling lands in VFR, MVFR, IFR, or LIFR.

Last updated June 29, 2026