A METAR is written as a fixed sequence of groups, so once you know the order you can read any report. Using the example above (KJFK 041851Z 24015G25KT 10SM -RA FEW045 BKN120 OVC250 22/14 A2992):
- Report type:
METAR for a routine report, SPECI for a special one issued between routine reports. Data feeds often leave it out. - Station: the four-letter ICAO code of the airport,
KJFK. - Date and time:
041851Z is the 4th day of the month at 18:51 UTC. - Modifier, if any:
AUTO for a fully automated report, COR for a correction. - Wind:
24015G25KT is from 240° true at 15 knots, gusting to 25. 00000KT is calm, VRB is variable, and 200V270 means the direction is varying between 200° and 270°. - Visibility:
10SM is 10 statute miles (US). Most other countries report metres, where 9999 means 10 km or more. - Runway visual range, in low visibility:
R04R/2200FT is 2,200 ft along runway 04R. - Present weather:
-RA is light rain. Groups combine an intensity, a descriptor and a phenomenon (see the tables below). - Sky condition: cloud amount plus base height in hundreds of feet above ground.
FEW045 is a few clouds at 4,500 ft. The ceiling is the lowest broken (BKN), overcast (OVC) or obscured (VV) layer — here BKN120, 12,000 ft. - Temperature and dew point in °C:
22/14. An M means minus (M05 = −5 °C). When the two are within about 3 °C, fog and low cloud become likely. - Pressure:
A2992 is an altimeter setting of 29.92 inHg (US and Canada); Q1013 is QNH in hectopascals. - Remarks: everything after
RMK. US stations add sensor details, sea-level pressure and precise temperatures here.
US and international METARs
The code is international, but the US uses a few national variations you need to recognise:
| United States | Most other countries |
|---|
| Visibility | Statute miles: 10SM, 1/2SM | Metres: 9999, 0800 |
| Pressure | A2992: inches of mercury | Q1013: hectopascals |
| No cloud | CLR (automated, none below 12,000 ft) or SKC | NSC, NCD or CAVOK |
| End of report | Detailed RMK section (AO2, SLP, T-group) | Often a 2-hour trend: NOSIG, BECMG, TEMPO |
How to read a TAF
A TAF starts with a header — TAF KJFK 041720Z 0418/0524 — giving the airport, the issue time (the 4th at 17:20 UTC) and the validity period (from the 4th at 18:00 to the 5th at 24:00 UTC). In the US, TAFs are issued four times a day and amended when the forecast changes; they cover 24 or 30 hours.
The first forecast group uses the same wind, visibility, weather and cloud codes as a METAR (P6SM means more than 6 statute miles). Change groups then say how and when conditions change:
| Group | Meaning |
|---|
FM050200 | From the 5th at 02:00 UTC: a rapid change. Everything after it replaces the earlier forecast. |
BECMG 0506/0508 | Becoming: a gradual change during the period, after which the new conditions persist. |
TEMPO 0418/0422 | Temporarily: fluctuations, each lasting under an hour and together less than half the period. |
PROB30 0510/0514 | A 30% (or PROB40, 40%) chance of the conditions that follow during the period. |
WS020/24045KT | Low-level wind shear (US TAFs): at 2,000 ft above ground, wind from 240° at 45 kt. |
Flight categories
The decoder labels each observation and forecast period with the flight category used on Aviation Weather Center charts. It is set by whichever is worse, the ceiling or the visibility:
| Category | Ceiling | Visibility |
|---|
| VFR | Above 3,000 ft | Above 5 statute miles |
| MVFR | 1,000 to 3,000 ft | 3 to 5 statute miles |
| IFR | 500 to below 1,000 ft | 1 to below 3 statute miles |
| LIFR | Below 500 ft | Below 1 statute mile |
These categories summarise conditions; they are not the same thing as the legal VFR weather minimums for your airspace.
Weather codes
A present-weather group is built as intensity + descriptor + phenomenon: +TSRA is a heavy thunderstorm with rain, FZFG is freezing fog, VCSH is showers in the vicinity.
| Code | Meaning |
|---|
- | Light |
| (none) | Moderate |
+ | Heavy (or well-developed, for dust whirls and funnel clouds) |
VC | In the vicinity: near the airport but not at it |
RE | Recent: ended within the past hour (e.g. RERA) |
MI | Shallow |
PR | Partial |
BC | Patchy |
DR | Low drifting |
BL | Blowing |
FZ | Freezing |
SH | Showers |
TS | Thunderstorm |
| Code | Phenomenon |
|---|
DZ | Drizzle |
RA | Rain |
SN | Snow |
SG | Snow grains |
IC | Ice crystals |
PL | Ice pellets |
GR | Hail |
GS | Small hail |
UP | Unknown precipitation |
BR | Mist |
FG | Fog |
FU | Smoke |
VA | Volcanic ash |
DU | Dust |
SA | Sand |
HZ | Haze |
PY | Spray |
PO | Dust whirls |
SQ | Squalls |
FC | Funnel cloud |
SS | Sandstorm |
DS | Duststorm |
Cloud cover codes
| Code | Meaning |
|---|
SKC | Sky clear |
CLR | No clouds below 12,000 ft (automated US stations, which can't detect higher) |
NSC | No significant cloud: none below 5,000 ft and no cumulonimbus or towering cumulus |
NCD | No cloud detected (automated stations) |
FEW | Few: 1–2 oktas (eighths) of the sky |
SCT | Scattered: 3–4 oktas |
BKN | Broken: 5–7 oktas, counts as a ceiling |
OVC | Overcast: 8 oktas, counts as a ceiling |
VV | Vertical visibility into an obscured sky (fog, snow), counts as a ceiling |
CB / TCU | Cumulonimbus / towering cumulus, appended to a layer (e.g. BKN030CB) |
| Remark | Meaning |
|---|
AO1 / AO2 | Automated station without / with a precipitation discriminator |
SLP132 | Sea-level pressure 1013.2 hPa |
T02220139 | Temperature 22.2 °C and dew point 13.9 °C, to a tenth of a degree (1 = minus) |
PK WND 25030/1820 | Peak wind from 250° at 30 kt, at 18:20 UTC |
WSHFT 30 FROPA | Wind shift at :30 past the hour, with a frontal passage |
RAB15E30 | Rain began at :15 and ended at :30 past the hour |
P0001 | Precipitation in the past hour: 0.01 in (P0000 = a trace) |
60012 / 70045 | Precipitation in the past 3 or 6 hours / 24 hours, in hundredths of an inch |
10222 / 20111 | Highest / lowest temperature in the past 6 hours, in tenths of °C |
51015 | 3-hour pressure tendency: rising then steady, 1.5 hPa |
TSNO, PNO, RVRNO | A sensor (lightning, precipitation amount, RVR) isn't available |
$ | The station needs maintenance |
Frequently asked questions
- What is a METAR?
- A METAR is a routine aviation weather observation from an airport, in the international format defined by the World Meteorological Organization (WMO) and ICAO. Each report gives the wind, visibility, present weather, clouds, temperature, dew point and pressure at one airport at one moment.
- How often are METARs issued?
- Most airports issue a routine METAR every hour, and many outside the US issue one every 30 minutes. In between, a SPECI (special report) is issued whenever conditions change significantly — for example when the ceiling or visibility crosses a threshold or a thunderstorm begins.
- What is the difference between a METAR and a TAF?
- A METAR reports the weather observed at the airport right now. A TAF (Terminal Aerodrome Forecast) forecasts the weather expected within 5 statute miles of the airport over the next 24 or 30 hours, including when conditions are expected to change.
- What time zone are METAR and TAF times in?
- Always UTC, also called Zulu time — the Z at the end of the time group. 041851Z means the 4th day of the month at 18:51 UTC. Convert to local time yourself.
- What does CAVOK mean?
- Ceiling And Visibility OK: visibility of 10 km or more, no cloud below 5,000 ft (or below the highest minimum sector altitude, if that is higher), no cumulonimbus or towering cumulus, and no significant weather. It is used outside the US in place of the visibility, weather and cloud groups.
- Why is the METAR wind direction different from the ATIS?
- METAR and TAF wind directions are measured from true north. ATIS and the control tower give wind relative to magnetic north, to match the runway headings. The difference is the local magnetic variation.
- What do AUTO and AO2 mean in a METAR?
- AUTO means the report was produced by an automated station with no human observer. AO2 in the remarks means the automated station has a precipitation discriminator and can tell rain from snow; AO1 means it can't.
- Can I use this decoder for flight planning?
- Use it to learn and to check your reading of a report, not as a briefing. Always get an official weather briefing and check current NOTAMs, ATIS and ATC information before a flight.
Decoded live weather by airport
Every airport page shows the current METAR and TAF already decoded, with runway wind components and the flight category. A few busy airports to start with:
Or browse airports by country.
Sources
The decoder follows the WMO code forms for METAR and TAF (WMO-No. 306, Manual on Codes; ICAO Annex 3) and the US conventions in FAA Advisory Circular 00-45, Aviation Weather Services, and the Federal Meteorological Handbook No. 1. Live reports come from the NOAA Aviation Weather Center. Read how Aeronuvia uses this data.
For learning and reference only. Not an official weather briefing.