For current reports, use your national meteorological service or the U.S. Aviation Weather Center (aviationweather.gov).
What is a METAR?
A METAR is a routine aerodrome weather observation, normally issued every 30 or 60 minutes. It uses a compact code defined by the World Meteorological Organization (WMO) and ICAO. A special report (SPECI) is issued when conditions change significantly between routine reports.
How to read a METAR, group by group
Reports follow a fixed order: station identifier (ICAO code), day and time in UTC, wind, visibility, runway visual range, present weather, clouds, temperature/dew point, pressure (QNH), and optional trend and remarks. For example, “EGLL 091250Z 24012KT 9999 FEW030 12/07 Q1015” means London Heathrow on the 9th at 12:50 UTC, wind from 240° at 12 knots, visibility 10 km or more, few clouds at 3,000 ft, 12 °C, dew point 7 °C, QNH 1015 hPa.
What is a TAF?
A Terminal Aerodrome Forecast (TAF) describes expected conditions at an airport, usually for 9 to 30 hours. It uses the same groups as a METAR plus change indicators: FM (from a time), BECMG (gradual change), TEMPO (temporary fluctuations) and PROB30/PROB40 (probability of a condition).
Visibility and fog
Visibility is reported in metres in most of the world (9999 = 10 km or more) and in statute miles in the United States (for example 1/2SM). Mist (BR) is reported with visibility from 1,000 m to 5,000 m; fog (FG) when visibility falls below 1,000 m. Fog forms when the air cools to its dew point, so a small temperature–dew point spread is an early warning sign.
Wind and gusts
Wind is given as the direction it blows from (true degrees), followed by speed: 27015G28KT means from 270° at 15 knots gusting 28 knots. VRB indicates variable direction and 00000KT calm. Crosswind and tailwind components relative to the runway matter more to pilots than the total wind.
Clouds and ceiling
Cloud cover is reported in oktas (eighths of sky): FEW, SCT, BKN and OVC, with the base height in hundreds of feet above the aerodrome. The ceiling is the lowest broken (BKN) or overcast (OVC) layer, or the vertical visibility (VV) when the sky is obscured.
VFR, MVFR, IFR and LIFR
Flight categories summarise ceiling and visibility. Under the U.S. FAA thresholds: VFR — ceiling above 3,000 ft and visibility above 5 miles; MVFR — ceiling 1,000–3,000 ft or visibility 3–5 miles; IFR — ceiling 500 to below 1,000 ft or visibility 1 to below 3 miles; LIFR — ceiling below 500 ft or visibility below 1 mile. Other countries apply their own rules for visual flight.
Flight category thresholds (FAA)
| Ceiling | Visibility | |
|---|---|---|
| VFR VFR — visual flight rules | > 3,000 ft | > 5 SM |
| MVFR Marginal VFR | 1,000–3,000 ft | 3–5 SM |
| IFR IFR — instrument flight rules | 500–999 ft | 1–< 3 SM |
| LIFR Low IFR | < 500 ft | < 1 SM |
Pressure: QNH and inHg
QNH is the altimeter setting that makes an altimeter read the aerodrome’s elevation on the ground. It is reported in hectopascals (Q1013) in most countries and in inches of mercury (A2992) in North America. Standard pressure is 1013.25 hPa = 29.92 inHg.
Glossary
- AUTO
- Fully automated report with no human intervention.
- CAVOK
- Ceiling and visibility OK: visibility 10 km or more, no cloud below 5,000 ft or minimum sector altitude, no significant weather.
- NOSIG
- No significant change expected in the next two hours.
- QNH
- Altimeter setting giving elevation above mean sea level.
- RVR
- Runway visual range: how far a pilot can see along the runway.
- SPECI
- Special unscheduled report issued after a significant change.
- TEMPO
- Temporary fluctuations expected for less than an hour at a time.
- UTC / Z
- Coordinated Universal Time, “Zulu”, used for all aviation times.