Complete Guide to Aviation Weather Reporting Codes and Abbreviations

Decode every weather symbol, code, and abbreviation you'll encounter in aviation

Last updated: May 6, 2026 | Reading time: 3 minutes | 912 words

Table of Contents

1. Understanding Aviation Weather Code Structure

Aviation weather reporting uses standardized codes and abbreviations to communicate meteorological conditions efficiently and unambiguously across international boundaries. These pilot weather reporting codes follow specific formats established by the International Civil Aviation Organization (ICAO) and the World Meteorological Organization (WMO).

Weather codes serve multiple purposes in aviation: they provide current conditions through METAR reports, forecast future conditions via TAF messages, and relay real-time observations through PIREP communications. Each code type follows distinct formatting rules and uses specific abbreviations that pilots must understand for safe flight operations.

Key Point

All aviation weather codes use UTC time and standardized abbreviations to ensure consistent interpretation worldwide, regardless of local language or customs.

The foundation of weather code literacy begins with recognizing that each element has a specific position and format. Unlike narrative weather descriptions, codes compress maximum information into minimum space while maintaining precision essential for flight safety decisions.

2. METAR Code Components and Abbreviations

METAR reports contain standardized sections, each with specific abbreviations and formats. Understanding these components enables pilots to extract critical weather information quickly during flight planning and operations.

METAR KORD 231651Z 27015G23KT 10SM FEW050 BKN180 06/M08 A3012 RMK AO2 SLP225

Station Identification: Four-letter ICAO identifiers (KORD = Chicago O'Hare) begin each METAR. US stations start with 'K', Canadian with 'C', and international codes vary by region.

Time Group: Six digits represent day and UTC time (231651Z = 23rd day, 1651 UTC). The 'Z' suffix indicates Zulu (UTC) time.

Wind Information: Five or six digits plus 'KT' show direction and speed (27015KT = 270° at 15 knots). Gusts appear as 'G' plus maximum speed (27015G23KT). Variable winds show as 'VRB' and calm winds as '00000KT'.

Visibility: Statute miles in US (10SM = 10 statute miles) or meters internationally. Fractions appear as '1/2SM' or whole numbers. 'P6SM' indicates visibility greater than 6 statute miles.

For a comprehensive breakdown of METAR interpretation, see our complete METAR reading guide.

3. Weather Phenomenon Abbreviations

Weather phenomena use two-letter combinations describing intensity, descriptor, precipitation, and obscuration types. These codes appear in both METAR and TAF reports.

Intensity Indicators:

  • '-' = Light intensity
  • No prefix = Moderate intensity
  • '+' = Heavy intensity
  • 'VC' = In vicinity (5-10 miles from station)

Descriptors:

  • MI = Shallow
  • PR = Partial
  • BC = Patches
  • DR = Low drifting
  • BL = Blowing
  • SH = Showers
  • TS = Thunderstorm
  • FZ = Freezing

Precipitation Types:

  • DZ = Drizzle
  • RA = Rain
  • SN = Snow
  • SG = Snow grains
  • IC = Ice crystals
  • PE = Ice pellets
  • GR = Hail
  • GS = Small hail/snow pellets

Caution

Freezing precipitation (FZRA, FZDZ) creates immediate hazards for aircraft without anti-ice systems. Always check for freezing level information when encountering these codes.

Obscuration and Other Phenomena:

  • FG = Fog
  • BR = Mist
  • HZ = Haze
  • FU = Smoke
  • DU = Dust
  • SA = Sand
  • PO = Dust/sand whirls
  • SQ = Squalls
  • FC = Funnel cloud/tornado
  • SS = Sandstorm

4. Cloud Coverage and Type Abbreviations

Cloud reporting follows specific abbreviations for coverage amounts and cloud types, critical for determining flight categories and ceiling conditions.

Coverage Abbreviations:

  • SKC/CLR = Sky clear (SKC = human observer, CLR = automated)
  • FEW = Few clouds (1/8 to 2/8 coverage)
  • SCT = Scattered clouds (3/8 to 4/8 coverage)
  • BKN = Broken clouds (5/8 to 7/8 coverage)
  • OVC = Overcast (8/8 coverage)
  • VV = Vertical visibility (obscured sky)

Heights follow coverage indicators in hundreds of feet AGL. For example: 'FEW050' indicates few clouds at 5,000 feet AGL.

Cloud Type Suffixes:

  • TCU = Towering cumulus
  • CB = Cumulonimbus
  • ACC = Altocumulus castellanus
BKN015 OVC025 = Broken clouds at 1,500 feet, overcast at 2,500 feet

Special Cloud Conditions:

  • '///' = Cloud layer exists but height/coverage undetermined
  • '000' = Surface-based obscuration (fog, etc.)
  • Multiple layers listed from lowest to highest

Safety Note

Cumulonimbus (CB) and towering cumulus (TCU) indicators signal convective activity with potential severe turbulence, icing, and wind shear hazards.

5. TAF Forecast Code Elements

Terminal Aerodrome Forecasts (TAF) use additional codes beyond METAR elements to indicate forecast changes and probabilities. These codes help pilots understand timing and likelihood of weather changes.

Change Indicators:

  • FM = From (permanent change at specified time)
  • BECMG = Becoming (gradual change over 2-4 hours)
  • TEMPO = Temporary (conditions lasting <1 hour, occurring >50% of time period)
  • PROB = Probability (PROB30 = 30% chance, PROB40 = 40% chance)

Time Formatting: TAF times use four-digit groups representing day and hour. 'BECMG 2414' means becoming conditions starting on the 24th at 14Z.

TAF KJFK 241720Z 2418/2524 31012KT P6SM FEW250 FM250200 28008KT

For detailed TAF interpretation techniques, reference our comprehensive TAF reading guide.

Conditional Terms:

  • NSW = No significant weather
  • NIL = No forecast issued
  • AMD = Amended forecast
  • COR = Corrected forecast

6. PIREP Codes and Supplementary Weather Information

Pilot Reports (PIREPs) use specific abbreviations to communicate real-time flight conditions. These reports provide crucial information not available through automated weather systems.

Standard PIREP Elements:

  • UUA/UA = Urgent/Routine pilot report identifier
  • /OV = Location (over)
  • /TM = Time
  • /FL = Flight level/altitude
  • /TP = Aircraft type
  • /SK = Sky condition
  • /WX = Weather
  • /TA = Air temperature
  • /WV = Wind velocity
  • /TB = Turbulence
  • /IC = Icing
  • /RM = Remarks

Turbulence Reporting:

  • NEG = None (smooth)
  • LGT = Light
  • MOD = Moderate
  • SEV = Severe
  • EXTR = Extreme

Pro Tip

Always file PIREPs when encountering conditions significantly different from forecast, especially turbulence, icing, or unexpected cloud layers. Your report helps other pilots make informed decisions.

Icing Intensity Codes:

  • NEG = None
  • TRC = Trace
  • LGT = Light
  • MOD = Moderate
  • SEV = Severe

Icing Type Abbreviations:

  • RIME = Rime ice
  • CLR = Clear ice
  • MXD = Mixed ice

7. International Code Variations and Regional Differences

While aviation weather codes follow international standards, regional variations exist that pilots must understand for international operations.

Metric vs. Imperial Units:

  • US uses statute miles and inches Hg (altimeter setting)
  • International uses meters/kilometers and hectopascals/millibars
  • Temperature always in Celsius worldwide
  • Wind speeds in knots globally

Pressure Reporting Differences:

  • US: 'A3012' = 30.12 inches Hg
  • International: 'Q1019' = 1019 hectopascals

Visibility Variations:

  • US reports in statute miles (SM)
  • International reports in meters (9999 = 10km or greater)
  • Directional visibility may be specified internationally

Key Point

When planning international flights, always verify local weather reporting standards and unit conversions to avoid misinterpretation of critical weather information.

European Additions:

  • CAVOK = Ceiling and visibility OK (visibility ≥10km, no clouds below 5,000ft, no significant weather)
  • Runway visual range (RVR) reported more frequently
  • Trend forecasts (NOSIG, BECMG, TEMPO) commonly appended to METAR

Frequently Asked Questions

What's the difference between CLR and SKC in weather reports?

CLR (clear) indicates no clouds detected by automated weather systems, while SKC (sky clear) means a human observer confirmed clear skies. CLR may miss thin or high clouds that automated systems can't detect.

How do I interpret wind gusts in aviation weather codes?

Wind gusts appear as 'G' followed by the maximum gust speed. For example, '27015G23KT' means wind from 270° at 15 knots with gusts to 23 knots. The gust value represents the peak speed, not sustained wind.

What does 'VC' mean in weather phenomenon codes?

'VC' means 'vicinity' and indicates the weather phenomenon is occurring within 5-10 miles of the reporting station but not at the station itself. For example, 'VCSH' means showers in the vicinity.

Why do some METARs show 'VV' instead of cloud layers?

'VV' indicates vertical visibility when the sky is obscured (usually by fog, snow, or other phenomena). The number following VV shows vertical visibility in hundreds of feet, such as 'VV002' meaning 200 feet vertical visibility.

How often should pilots file PIREPs?

File PIREPs whenever you encounter conditions significantly different from forecasts, especially turbulence, icing, or unexpected cloud layers. Routine reports help too, but urgent reports (UUA) are critical for hazardous conditions like severe turbulence or icing.