Report Type
| METAR | Routine hourly weather observation |
| SPECI | Special (unscheduled) observation due to significant weather changes |
| TAF | Terminal Aerodrome Forecast (weather forecast for an airport) |
Station Identifier
| KORD | 4-letter ICAO location identifier (K = contiguous US prefix) |
Date / Time
| 121755Z | Day 12, 17:55 UTC. Always in Zulu (UTC) time, suffixed with Z |
Modifier
| AUTO | Fully automated report, no human observer |
| COR | Correction to a previously issued report |
Wind
| 21016KT | Direction 210° true, speed 16 knots |
| G24KT | Gusting to 24 knots |
| VRB03KT | Variable direction at 3 knots |
| 00000KT | Calm (no wind) |
| 180V240 | Wind direction variable between 180° and 240° |
Visibility
| 10SM | 10 statute miles |
| 1/2SM | 1/2 statute mile |
| P6SM | Greater than 6 statute miles |
| M1/4SM | Less than 1/4 statute mile |
| 9999 | 10 km or more (ICAO format) |
Runway Visual Range (RVR)
| R11/P6000FT | Runway 11, RVR greater than 6,000 feet |
| R18L/1200FT | Runway 18 Left, RVR 1,200 feet |
| V | Variable (e.g., R11/1200V2000FT) |
Weather — Intensity
| - | Light |
| (none) | Moderate |
| + | Heavy |
| VC | In the vicinity (5–10 SM from airport) |
Weather — Descriptors
| MI | Shallow |
| PR | Partial |
| BC | Patches |
| DR | Low drifting |
| BL | Blowing |
| SH | Showers |
| TS | Thunderstorm |
| FZ | Freezing |
Weather — Precipitation
| RA | Rain |
| DZ | Drizzle |
| SN | Snow |
| SG | Snow grains |
| IC | Ice crystals |
| PL | Ice pellets |
| GR | Hail (≥1/4 inch) |
| GS | Small hail / snow pellets (<1/4 inch) |
| UP | Unknown precipitation (automated stations) |
Weather — Obscurations
| FG | Fog (visibility <5/8 SM) |
| BR | Mist (visibility 5/8–6 SM) |
| HZ | Haze |
| FU | Smoke |
| DU | Widespread dust |
| SA | Sand |
| VA | Volcanic ash |
| PY | Spray |
Weather — Other
| PO | Dust/sand whirls (dust devils) |
| SQ | Squall |
| FC | Funnel cloud / tornado / waterspout |
| SS | Sandstorm |
| DS | Duststorm |
Sky Condition
| SKC | Sky clear |
| CLR | Clear below 12,000 ft (automated stations) |
| FEW | Few clouds (1/8 – 2/8) |
| SCT | Scattered (3/8 – 4/8) |
| BKN | Broken (5/8 – 7/8) — ceiling |
| OVC | Overcast (8/8) — ceiling |
| VV | Vertical visibility (sky obscured), e.g. VV005 = 500 ft |
| CB | Cumulonimbus (suffix, e.g. BKN040CB) |
| TCU | Towering cumulus (suffix) |
Height is in hundreds of feet AGL. BKN015 = broken clouds at 1,500 ft. Multiple layers may be reported.
Temperature / Dewpoint
| 06/04 | Temperature 6°C, dewpoint 4°C |
| M02/M08 | Temperature −2°C, dewpoint −8°C (M = minus) |
Temp-dewpoint spread: When the spread narrows to 2–3°C, expect fog, mist, or low clouds.
Altimeter Setting
| A2990 | 29.90 inches of mercury (inHg) — US format |
| Q1013 | 1013 hectopascals (hPa) — ICAO format |
Remarks (RMK)
| AO1 | Automated station without precipitation discriminator |
| AO2 | Automated station with precipitation discriminator |
| SLP125 | Sea-level pressure: 1012.5 hPa |
| T00640036 | Precise temp 6.4°C, dewpoint 3.6°C |
| PK WND | Peak wind: direction, speed, and time |
| WSHFT | Wind shift at specified time |
| PRESFR | Pressure falling rapidly |
| PRESRR | Pressure rising rapidly |
| P0003 | Hourly precipitation: 0.03 inches |
| TSNO | Thunderstorm info not available |
| $ | Station needs maintenance |
TAF — Valid Period
| 1318/1424 | Valid from day 13 at 18Z to day 14 at 24Z |
TAF — Change Groups
| FM130200 | From day 13 at 02:00Z — permanent change to new conditions |
| BECMG | Becoming — gradual change over a time period |
| TEMPO | Temporary — fluctuations lasting <1 hour at a time |
| PROB30 | 30% probability of conditions |
| PROB40 | 40% probability of conditions |
| AMD | Amended forecast (replaces previous TAF) |
| CAVOK | Ceiling & visibility OK (≥10 km vis, no sig. clouds/weather) |
| NSW | No significant weather (cancels previous weather) |