What do FEW, SCT, BKN, and OVC mean in a METAR?

They describe sky cover in oktas, or eighths of the sky. FEW is 1 to 2 oktas, SCT (scattered) is 3 to 4, BKN (broken) is 5 to 7, and OVC (overcast) is a full 8 oktas. BKN and OVC layers form a ceiling, the lowest layer that obscures more than half the sky.

What does CAVOK mean?

CAVOK stands for Ceiling And Visibility OK. It is reported when visibility is 10 km or more, there is no cloud below 5,000 feet or below the highest minimum sector altitude, and there is no significant weather. It is a shorthand for benign conditions.

How are weather phenomena built up in a METAR?

A weather group is read left to right as intensity, then descriptor, then phenomenon. A minus sign means light and a plus sign means heavy. So +SHRA is heavy rain showers, FZFG is freezing fog, and VCTS is a thunderstorm in the vicinity of the airfield.

What is the difference between BR and FG?

Both are reductions in visibility from suspended water droplets. BR is mist, reported when visibility is between 1,000 and 5,000 metres. FG is fog, reported when visibility drops below 1,000 metres. The threshold is purely the prevailing visibility.

Do TAF forecasts use the same codes as METAR?

Yes. A TAF (Terminal Aerodrome Forecast) uses the same sky cover, precipitation, and obscuration codes as a METAR observation. TAFs add change groups such as BECMG for a lasting change and TEMPO for short-lived fluctuations to describe how conditions will evolve.

What is the METAR Abbreviation Reference?

Searchable reference of METAR and TAF abbreviations covering sky cover (FEW, SCT, BKN, OVC, CAVOK), precipitation, obscurations, descriptors, intensity prefixes, and trend codes, with the meaning of each code grouped by category. It runs free in your browser on Gera Tools, with nothing uploaded.

METAR Abbreviation Reference

Name: METAR Abbreviation Reference
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Reading a METAR

A METAR is a coded aerodrome weather observation, and a TAF is its forecast cousin. Both pack sky cover, visibility, weather phenomena, and wind into terse abbreviations. This reference lists the common codes grouped by category — sky cover, intensity and proximity, descriptors, precipitation, obscurations, other phenomena, wind, and trend — and lets you filter by code or plain English.

How it works

Weather groups are not random letters; they follow a fixed order so they can be read mechanically:

[intensity][descriptor][phenomenon]
-          light          minus sign
+          heavy          plus sign
SH RA  ->  rain showers
FZ FG  ->  freezing fog
VC TS  ->  thunderstorm in the vicinity

Sky cover is reported in oktas (eighths): FEW, SCT, BKN, OVC, climbing from a couple of clouds to a fully overcast sky. A BKN or OVC layer counts as a ceiling. Wind adds G for gusts and KT for knots, e.g. 24018G30KT is wind from 240 degrees at 18 knots gusting 30.

Decoding a real METAR — a step-by-step example

Take this sample report:

EGLL 151220Z 25015G25KT 9999 -RA SCT018 BKN035 12/08 Q1008 NOSIG

Reading it left to right:

EGLL — station identifier (London Heathrow)
151220Z — 15th of the month, 12:20 UTC
25015G25KT — wind from 250 degrees at 15 knots, gusting 25 knots
9999 — visibility 10 km or more
-RA — light rain (minus = light, RA = rain)
SCT018 — scattered cloud at 1,800 feet
BKN035 — broken layer at 3,500 feet (this is the ceiling)
12/08 — temperature 12 °C, dew point 8 °C
Q1008 — altimeter setting 1008 hPa (QNH)
NOSIG — no significant change expected in the next two hours

Notice that BKN (broken, 5–7 oktas) forms the ceiling because it is the lowest layer covering more than half the sky.

Visibility and ceiling thresholds at a glance

Condition	Visibility	Ceiling
CAVOK	10 km+	No cloud below 5,000 ft, no wx
Visual meteorological (VMC rough guide)	5 km+	1,500 ft+
Instrument meteorological (IMC)	Below VMC minima	Below VMC minima
LIFR (low IFR)	Below 1 mile	Below 500 ft

These are indicative reference values; actual minima vary by approach type and authority.

Tips and notes

CAVOK collapses several good-weather conditions into one word, while NOSIG, BECMG, and TEMPO describe how conditions are expected to change. The RMK keyword introduces a remarks section that, in US reports, carries extra automated data after the main body. When intensity qualifiers are absent, the phenomenon is moderate — so RA alone means moderate rain, not light and not heavy.

The letter pairs to memorise first are the common ones: RA (rain), SN (snow), TS (thunderstorm), FG (fog), BR (mist), DZ (drizzle), FZ (freezing), SH (shower), VC (in vicinity). Everything else is built by combining them with intensity and descriptor prefixes from this same reference.