Aviation Weather Code Reference

One short page per code. Each one answers what it means in the first sentence, then shows it in a real report and explains what it changes for you. Whole-format references: PIREP codes, SIGMET codes and military TAF codes. Want it decoded for you instead? Paste any report into the decoder.

Report basics

AUTO in a METAR: Meaning and Examples

a fully automated report with no human observer involved

COR in a METAR: Meaning and Examples

a correction to a previously transmitted report

P6SM in a TAF: Meaning and Examples

visibility greater than 6 statute miles. P before a value means "more than"

RMK in a METAR: Meaning and Examples

remarks identifier: everything after it is the remarks section

Present weather

VC in a METAR: Meaning and Examples

in the vicinity: within 5 to 10 SM of the airport, but not at it

BR in a METAR: Meaning and Examples

mist

FG in a METAR: Meaning and Examples

fog

FU in a METAR: Meaning and Examples

smoke

VA in a METAR: Meaning and Examples

volcanic ash

HZ in a METAR: Meaning and Examples

haze

SH in a METAR: Meaning and Examples

showers

TS in a METAR: Meaning and Examples

thunderstorm

FZ in a METAR: Meaning and Examples

freezing

Cloud and ceiling

SKC in a METAR or TAF: Meaning and Examples

sky clear (reported by a human observer)

CLR in a METAR: Meaning and Examples

no clouds detected below 12,000 ft (automated stations)

FEW in a METAR: Meaning and Examples

few clouds: 1 to 2 oktas (eighths) of sky cover

SCT in a METAR: Meaning and Examples

scattered clouds: 3 to 4 oktas of sky cover

BKN in a METAR: Meaning and Examples

broken clouds: 5 to 7 oktas; the lowest broken layer is a ceiling

OVC in a METAR: Meaning and Examples

overcast: 8 oktas, full sky cover; an overcast layer is a ceiling

VV in a METAR: Meaning and Examples

vertical visibility: how far you can see upward into an obscuration such as fog or heavy snow. There is no cloud base, and the VV height acts as an indefinite ceiling

CIG in a METAR: Meaning and Examples

ceiling: the lowest broken (BKN) or overcast (OVC) layer, or vertical visibility (VV). FEW and SCT are never ceilings

CB in a METAR: Meaning and Examples

cumulonimbus: thunderstorm cloud; severe turbulence, icing and wind-shear hazard

TCU in a METAR: Meaning and Examples

towering cumulus: a building storm cloud, often a thunderstorm precursor

Wind and visibility

PK WND in a METAR: Meaning and Examples

peak wind since the last METAR: direction, speed, and the time it occurred

WSHFT in a METAR: Meaning and Examples

wind shift: the time the wind direction changed by 45° or more

FROPA in a METAR: Meaning and Examples

frontal passage: a front moved across the station

Pressure and temperature

PRESRR in a METAR: Meaning and Examples

pressure rising rapidly at observation time

PRESFR in a METAR: Meaning and Examples

pressure falling rapidly, often a storm or front approaching

Station and sensor status

AO1 in a METAR: Meaning and Examples

automated station without a precipitation discriminator (cannot tell rain from snow)

AO2 in a METAR: Meaning and Examples

automated station with a precipitation discriminator (can tell rain from snow)

TAF groups

TEMPO in a TAF: Meaning and Examples

temporary fluctuations lasting less than an hour at a time during the period given

BECMG in a TAF: Meaning and Examples

a gradual change over the period given; after it, the new conditions prevail

PROB30 in a TAF: Meaning and Examples

a 30% probability of the conditions during the period: possible, not expected

NSW in a TAF: Meaning and Examples

no significant weather: the previous weather has ended

International codes

CAVOK in a METAR or TAF: Meaning and Examples

ceiling and visibility OK: visibility 10 km or more, no cloud below 5,000 ft, no CB, no significant weather

9999 in a METAR or TAF: Meaning and Examples

visibility 10 kilometers or more (international meters format)