Aviation Weather Glossary

Comprehensive reference for aviation weather terms and codes

Last updated: May 6, 2026 | 102+ terms

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Weather Reports & Forecasts Cloud Types & Coverage Visibility & Obscurations Precipitation Types Weather Phenomena Wind Terms Pressure & Altimetry Temperature Terms TAF Change Groups Flight Categories Remarks & Codes NOTAM Terms

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Weather Reports & Forecasts

METAR Meteorological Aerodrome Report - A standardized format for reporting weather observations at airports, typically issued hourly.
SPECI Special METAR - An unscheduled weather observation issued when significant weather changes occur between regular METAR times.
TAF Terminal Aerodrome Forecast - A weather forecast for the area within 5 statute miles of an airport runway complex, valid for 24-30 hours.
SIGMET Significant Meteorological Information - Advisory for weather phenomena potentially hazardous to all aircraft: severe turbulence, icing, volcanic ash.
AIRMET Airman's Meteorological Information - Advisory for weather phenomena potentially hazardous to light aircraft: moderate turbulence/icing, IFR conditions, mountain obscuration.
PIREP Pilot Report - Weather observations made by pilots in flight, providing real-time conditions that may not appear in surface observations.
FA Area Forecast - A forecast of general weather conditions over a large region.
TWEB Transcribed Weather Broadcast - Recorded weather information available by phone or radio.

Cloud Types & Coverage

SKC Sky Clear - No clouds present (manual observation).
CLR Clear - No clouds below 12,000 feet (automated observation).
FEW Few clouds - 1/8 to 2/8 sky coverage (1-2 oktas).
SCT Scattered - 3/8 to 4/8 sky coverage (3-4 oktas). Not a ceiling.
BKN Broken - 5/8 to 7/8 sky coverage (5-7 oktas). Constitutes a ceiling.
OVC Overcast - 8/8 sky coverage (8 oktas). Full cloud cover.
VV Vertical Visibility - Height into an obscured sky (fog, heavy precipitation).
CB Cumulonimbus - Thunderstorm cloud. Indicates convective activity, severe turbulence, lightning, hail possible.
TCU Towering Cumulus - Tall cumulus cloud indicating developing convection. May become CB.
CEILING The height of the lowest layer of clouds reported as broken (BKN) or overcast (OVC), or vertical visibility into an obscured sky.

Visibility & Obscurations

SM Statute Miles - Unit of visibility measurement in US METARs.
KM Kilometers - Unit of visibility measurement in international METARs.
9999 Visibility 10 km or more (international METARs) - Essentially unlimited visibility.
FG Fog - Visibility less than 5/8 statute mile due to water droplets.
BR Mist - Visibility 5/8 mile to 6 miles due to water droplets.
HZ Haze - Visibility reduction due to fine particles (dust, smoke, pollution).
FU Smoke - Visibility reduction due to combustion products.
DU Dust - Widespread dust reducing visibility.
SA Sand - Sand particles in the air reducing visibility.
VA Volcanic Ash - Particulates from volcanic eruption. Extremely hazardous to aircraft.
PY Spray - Water spray reducing visibility (usually near waterfalls or large bodies of water).

Precipitation Types

RA Rain - Liquid precipitation.
DZ Drizzle - Fine liquid precipitation (drops less than 0.5mm).
SN Snow - Frozen precipitation in crystalline form.
SG Snow Grains - Very small, flat, opaque ice particles.
IC Ice Crystals - Tiny ice crystals (diamond dust) visible in very cold conditions.
PL Ice Pellets - Frozen rain that bounces on impact (sleet).
GR Hail - Ice balls 5mm or greater in diameter.
GS Small Hail/Snow Pellets - Ice particles less than 5mm.
UP Unknown Precipitation - Automated stations cannot determine precipitation type.
FZRA Freezing Rain - Rain that freezes on contact with cold surfaces. Severe icing hazard.
FZDZ Freezing Drizzle - Drizzle that freezes on contact. Icing hazard.

Weather Phenomena

TS Thunderstorm - Convective activity with lightning. Often accompanied by gusty winds, heavy precipitation, hail.
SH Showers - Precipitation from convective clouds. Characterized by rapid changes in intensity.
FZ Freezing - Prefix indicating supercooled water that freezes on contact.
MI Shallow - Fog or other phenomena extending less than 6 feet above ground.
PR Partial - Covering part of the airport but not all.
BC Patches - Fog or other phenomena occurring in patches.
DR Drifting - Snow or other particles being moved by wind but staying close to the ground.
BL Blowing - Snow, dust, or sand being raised well above the ground by wind.
SQ Squall - Sudden, sharp increase in wind speed lasting at least one minute.
FC Funnel Cloud - Rotating column of air extending from cloud base but not touching ground.
+FC Tornado or Waterspout - Funnel cloud that has reached the ground or water surface.
SS Sandstorm - Intense dust/sand storm significantly reducing visibility.
DS Duststorm - Storm with dust reducing visibility below 1000 meters.
PO Dust/Sand Whirls - Well-developed rotating columns of dust or sand.

Wind Terms

KT Knots - Unit of wind speed (1 knot = 1.15 mph = 1.85 km/h).
MPS Meters Per Second - Alternative wind speed unit used internationally.
G Gusts - Rapid fluctuations in wind speed. Reported when peak exceeds sustained by 10+ knots.
VRB Variable - Wind direction varying too much to assign a single direction (usually with speeds < 6 knots).
00000KT Calm - Wind speed less than 1 knot.
WSHFT Wind Shift - Significant change in wind direction.
PK WND Peak Wind - Maximum instantaneous wind speed recorded.
WS Wind Shear - Sudden change in wind speed and/or direction. Hazardous on approach/departure.

Pressure & Altimetry

A Altimeter Setting (US) - Atmospheric pressure in inches of mercury (e.g., A3012 = 30.12" Hg).
Q Altimeter Setting (International) - Atmospheric pressure in hectopascals (e.g., Q1013 = 1013 hPa).
SLP Sea Level Pressure - Atmospheric pressure reduced to sea level, in hectopascals (e.g., SLP203 = 1020.3 hPa).
PA Pressure Altitude - Altitude indicated when altimeter is set to 29.92" Hg (standard pressure).
DA Density Altitude - Pressure altitude corrected for non-standard temperature. Affects aircraft performance.
ISA International Standard Atmosphere - Standard conditions: 15°C at sea level, 29.92" Hg, lapse rate 2°C/1000ft.

Temperature Terms

T Temperature - Reported in degrees Celsius in METARs.
DP Dewpoint - Temperature at which air becomes saturated and condensation occurs.
M Minus/Below Zero - Prefix for temperatures below 0°C (e.g., M05 = -5°C).
SPREAD Temperature-Dewpoint Spread - Difference between temperature and dewpoint. Small spread indicates high humidity.

TAF Change Groups

FM From - Complete change in conditions expected at specified time.
TEMPO Temporary - Temporary fluctuations expected to last less than one hour each time.
BECMG Becoming - Gradual change in conditions expected over 2-hour period.
PROB Probability - Likelihood of conditions occurring (usually 30% or 40%).
NSW No Significant Weather - No weather phenomena expected.
NOSIG No Significant Change - Trend indicator meaning conditions will persist.
CAVOK Ceiling And Visibility OK - Visibility 10km+, no clouds below 5000ft, no significant weather.

Flight Categories

VFR Visual Flight Rules - Ceiling > 3000 feet AND visibility > 5 statute miles. Best flying conditions.
MVFR Marginal VFR - Ceiling 1000-3000 feet AND/OR visibility 3-5 statute miles. Requires extra caution.
IFR Instrument Flight Rules - Ceiling 500-1000 feet AND/OR visibility 1-3 statute miles. Instrument rating required.
LIFR Low IFR - Ceiling < 500 feet AND/OR visibility < 1 statute mile. Most restrictive conditions.

Remarks & Codes

RMK Remarks - Additional information section of METAR.
AO1 Automated Observation Type 1 - Automated station without precipitation discriminator.
AO2 Automated Observation Type 2 - Automated station with precipitation discriminator.
PRESFR Pressure Falling Rapidly - Pressure dropped 0.06" Hg or more in past 3 hours.
PRESRR Pressure Rising Rapidly - Pressure rose 0.06" Hg or more in past 3 hours.
CIG Ceiling - Used in remarks for variable or secondary ceiling reports.
TWR VIS Tower Visibility - Visibility as observed from the control tower.
SFC VIS Surface Visibility - Visibility at ground level.
VIRGA Virga - Precipitation falling but evaporating before reaching the ground.

NOTAM Terms

NOTAM Notice to Air Missions - Official notices about conditions affecting flight safety.
TFR Temporary Flight Restriction - Airspace restriction for safety, security, or special events.
RWY Runway - The paved surface used for takeoff and landing.
TWY Taxiway - Paved surface for taxiing between runway and parking areas.
CLSD Closed - Facility or surface is not available for use.
OTS Out of Service - Equipment or facility temporarily unavailable.
U/S Unserviceable - Same as OTS, equipment not working.
PERM Permanent - NOTAM condition has no end date.
WEF With Effect From - Indicates when a condition begins.
TIL Until - Indicates when a condition ends.

Related Guides

How to Read METAR

Complete METAR decoding guide

How to Read TAF

Terminal forecast decoding guide

Flight Categories

VFR, MVFR, IFR, LIFR explained

Reading NOTAMs

Decode notices to air missions

Official References

NWS METAR/TAF Reference FAA AIM Chapter 7 - Meteorology Aviation Weather Center ICAO Standards

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Understanding Aviation Weather Terminology

Accurate weather interpretation is critical for flight safety. This comprehensive glossary covers essential terms from basic meteorological concepts to complex weather phenomena that affect aviation operations. Whether you're decoding METARs, TAFs, or analyzing weather reports, understanding these terms can make the difference between a safe flight and a weather-related incident.

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How to Use This Glossary

Quick Reference Tips

  • •Use the search function to quickly locate specific terms
  • •Category navigation helps browse related concepts
  • •Terms are cross-referenced with related weather concepts
  • •Bookmark this page for quick access during flight planning

Related Resources

Addresses common misunderstandings that could impact flight safety and adds educational value to the glossary

Common Weather Term Misconceptions

"Visibility" vs "Flight Visibility"

Ground visibility reported in METARs may differ from what pilots actually see in flight due to altitude and atmospheric conditions.

"Light" vs "Heavy" Precipitation

These terms have specific definitions in aviation weather - light rain can still significantly impact visibility and runway conditions.

"Ceiling" Interpretation

Ceiling refers to the lowest broken or overcast layer, not just any cloud layer. Scattered clouds don't constitute a ceiling.

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How to Use This Glossary

This comprehensive aviation weather glossary contains essential terms used in METAR, TAF, and other weather reports. Terms are organized by category for quick reference during flight planning and weather briefings.

Pro Tip: Bookmark this page and use the search function to quickly find specific terms while reviewing weather reports. Each definition includes context for how the term appears in actual aviation weather products.

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Understanding Aviation Weather Codes

METAR & TAF Basics

Weather reports use standardized codes and abbreviations established by the International Civil Aviation Organization (ICAO). These codes ensure consistent communication of critical weather information across all aviation facilities worldwide.

Example: BKN015 OVC025

Broken clouds at 1,500 feet, overcast at 2,500 feet

Common Patterns

  • •Wind information appears first in reports
  • •Visibility follows wind data
  • •Weather phenomena use 2-letter codes
  • •Cloud layers listed from lowest to highest
  • •Temperature and dewpoint in Celsius

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Critical Weather Terms

Certain weather terms indicate potentially hazardous conditions that require immediate pilot attention. Understanding these terms is essential for safe flight operations and regulatory compliance.

Key hazards include: Thunderstorms (TS), severe icing (IC), turbulence (TB), low-level wind shear (WS), and visibility restrictions below VFR minimums. Always consult current official weather sources for flight planning decisions.

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Understanding Aviation Weather Terminology

Aviation weather reports use standardized terminology and codes that are essential for flight safety. This glossary covers terms from METAR reports, TAF forecasts, and general meteorological phenomena that affect aviation operations. Mastering these terms is crucial for pilots, dispatchers, and aviation weather enthusiasts.

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How to Use This Glossary

Quick Search

Use the search box to instantly find specific terms across all categories. Perfect for looking up unfamiliar codes from weather reports.

Browse by Category

Navigate through organized sections covering weather phenomena, measurement units, reporting codes, and more.

Pro Tip

Bookmark this page for quick reference when reading weather reports. Terms are organized by frequency of use in aviation weather products.

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Quick Reference Guide

This glossary covers essential aviation weather terminology used in METARs, TAFs, PIREPs, and weather briefings. Each term includes practical context for real-world application in flight planning and weather interpretation.

For Student Pilots

Master the fundamentals of aviation weather terminology essential for your checkride and safe flying. Focus on METAR/TAF codes and basic weather phenomena.

For Experienced Pilots

Reference advanced meteorological terms, decode complex weather patterns, and understand nuanced reporting criteria for enhanced weather decision-making.

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How to Use This Glossary

1

Search or Browse

Use the search function above or browse by category to find specific terms quickly.

2

Understand Context

Each definition includes practical examples and usage context for real-world application.

3

Apply Knowledge

Practice with current weather reports to reinforce your understanding of each term.