Ctrl+Enter to decode
Paste any METAR or TAF report and get an instant plain-English breakdown of every token
→ Full METAR & Weather Reference GuideClick any example to load it into the decoder and decode it automatically.
A METAR (Meteorological Aerodrome Report) is a standardised format for reporting current surface weather conditions at an airport or aerodrome. Issued every 30–60 minutes, METARs encode wind, visibility, cloud cover, temperature, dew point and pressure into a compact string that pilots and dispatchers can decode at a glance. A SPECI is a special report issued when conditions change significantly between routine observations. Learn more in the full reference guide →
A METAR is read left to right and the groups always arrive in the same order, so once you know the running order you can read one without any decoder at all. Work through this report, which is a typical mid-morning observation for London Heathrow:
The four-letter ICAO location indicator for the observing aerodrome. The first letter is the world region (E covers northern Europe), the second the country (G is the United Kingdom), and the last two the individual aerodrome. There is no separate group saying "this is a routine report" here, because the word METAR is often stripped by the data source; if you see SPECI instead, the report was triggered by a significant change rather than the clock.
Day of the month, then the time in hours and minutes, then Z for UTC. This one was observed at 10:50 UTC on the 5th. Most aerodromes observe at 20 and 50 minutes past the hour, which is why 1050 and 1120 turn up so often. Always check the day as well as the clock. A cached report can be a day old and still look perfectly plausible on a page.
Wind from 240 degrees at 15 knots. METAR wind is referenced to true north, whereas the surface wind a controller passes over the radio is referenced to magnetic north. In the UK the variation is around one degree at present and the difference is noise; in northern Canada or Scandinavia it is not. Against runway 27 that wind is 30 degrees off the centreline, so the crosswind component is 15 × sin(30) = 7.5 kt. Gusts appear as 24015G28KT, and a separate 200V280 group means the direction is swinging between 200 and 280 degrees.
Prevailing visibility of 10 km or more. It is a ceiling on the reporting scale, not a statement that the air is unlimited. Below 10 km the visibility is given in metres on a stepped scale: 50 m steps up to 800 m, 100 m steps from 800 m to 5 km, then 1 km steps up to 10 km. So 0350 is 350 metres and 4000 is 4 km. North American reports use statute miles instead (10SM, 1/2SM).
Scattered cloud, 3 to 4 oktas, base 2,800 ft. That height is above aerodrome elevation, not above mean sea level. Heathrow sits at 83 ft, so the base is closer to 2,880 ft on the altimeter. A ceiling is defined as the lowest broken or overcast layer, so SCT028 on its own means there is no ceiling at all. Layers are listed lowest first, and CB or TCU is appended to the group when the observer sees it (SCT025CB).
Temperature 18 °C, dew point 12 °C, a spread of 6. Negative values carry an M (M02/M05). The spread is the fastest fog indicator you have: multiply it by roughly 400 to get an estimated convective cloud base in feet, so 6 × 400 = 2,400 ft, which is in the same neighbourhood as the reported 2,800 ft. A spread of 1 or 2 with light wind is how a clear evening becomes a diversion.
QNH of 1015 hPa. North American reports use inches of mercury with an A prefix (A2992). One hectopascal is worth about 27 ft of altimeter indication near sea level, so if you set 1013 instead of 1015 you will fly roughly 54 ft lower than you believe. On a non-precision approach with a 250 ft minimum that is not a rounding error.
VV003 is 300 ft of vertical visibility. VV/// means the sky is obscured and the system cannot measure how far up you can see, which is common at automatic stations. Reading it as "nothing there" inverts the meaning completely.R27L/0600 is runway visual range of 600 m on runway 27 left. An M prefix means less than the lowest reportable value (R27L/M0050), a P prefix means more than the highest (R27L/P2000), and a trailing U, D or N gives the ten-minute tendency: upward, downward, no change. RVR is reported when visibility or RVR drops below 1,500 m, so the mere presence of the group tells you something before you even read the number.TEMPO 0512/0516. In a METAR they belong to the trend forecast, which covers only the two hours after the observation, and they use FM, TL and AT with a four-figure time (TEMPO FM1130 TL1230 3000 RA). TEMPO means fluctuations each lasting under an hour and totalling less than half the period; BECMG means a permanent change is under way; NOSIG means nothing significant is expected in that two-hour window.Under the EASA NCO rules the commander has to be satisfied before departure that the flight can be conducted safely using the meteorological information available for the route, and that obligation is not discharged by glancing out of the clubhouse window. For a local VFR detail the practical minimum is the aerodrome METAR plus the TAF, read together: the METAR tells you what is happening now, the TAF tells you what the forecaster expects, and the two disagreeing is itself useful information.
Once an alternate is involved the reports do real legal work. Planning minima for a destination and its alternates are built from the TAF, while the METAR is what governs the approach on the day. If the reported RVR or visibility is below the applicable minimum for the approach you intend to fly, the approach may not be continued past the defined point (commonly the outer marker or 1,000 ft above the aerodrome), regardless of what the forecast promised three hours earlier.
Remember what a METAR actually is: an observation, taken at one place, at one moment, mostly by machines. A report timed 1050Z is already stale by 1150Z if a front is moving through. Decode it properly, then check how old it is, then look at the trend, then look outside.