How to Read a METAR, Group by Group

A METAR is a surface weather observation, taken near the top of the hour and coded in a fixed order, so a report from KRDU reads the same way as one from KSEA or PANC. The US format is set by the National Weather Service in Federal Meteorological Handbook No. 1 (FCM-H1-2019), explained for pilots in chapter 24 of the Aviation Weather Handbook (FAA-H-8083-28B), and summarized on one card in AIM 7-1-28 (AIM Basic with Change 3, effective July 9, 2026).

The report decoded below was composed for illustration in standard US format. It is not a real observation.

METAR KRDU 031851Z 24012G20KT 200V280 6SM -RA BR SCT012 BKN025 OVC060 18/16 A2985 RMK AO2 PK WND 25028/22 RAB15 PRESFR SLP108 P0004 T01780156

Raleigh-Durham, the 3rd at 1851 UTC. Wind 240 true at 12 gusting 20, swinging between 200 and 280. Six statute miles in light rain and mist. Scattered at 1,200, ceiling broken at 2,500, overcast at 6,000. Temperature 18, dew point 16, altimeter 29.85. The remarks say the station is automated with a precipitation sensor and the wind peaked at 28 knots at 22 past the hour. Rain began at 15 past, the pressure is falling fast, sea level pressure is 1010.8 hectopascals, four hundredths of an inch of rain has fallen since the last report, and the temperatures to a tenth are 17.8 and 15.6.

The order never changes

A US METAR carries up to 11 groups in the body, always in the same sequence, and a group that does not apply is left out rather than filled with a placeholder (FAA-H-8083-28B, 24.4.3). The sequence, from AIM 7-1-29, is type of report, station identifier, date and time, modifier, wind, visibility, runway visual range, weather, sky condition, temperature and dew point, altimeter, then remarks.

The omission rule is what trips up new readers. If nothing is falling and nothing restricts visibility, there is no weather group at all, and the sky condition follows the visibility directly. Find a group by its shape, not its position.

Two report types use this format. METAR is the routine hourly observation. SPECI is an unscheduled special observation, issued when something crosses a threshold between hours and containing every element a METAR does (FAA-H-8083-28B, 24.4.2). The triggers in Table 24-2 include a ceiling forming or moving through 3,000, 1,500, 1,000 or 500 feet; visibility crossing 3, 2, 1, one half or one quarter mile; a thunderstorm beginning or ending; and a wind shift of 45 degrees or more in under 15 minutes at 10 knots or more.

If you see one, the weather is changing.

Station, time and modifier

KRDU 031851Z is the station and the time of observation: the 3rd day of the month at 1851 UTC. The first two digits are the day, the next four are hours and minutes, and the Z means UTC (FAA-H-8083-28B, 24.4.3.3). A report taken at 1851 is disseminated as the 1900 report. Day first, always: 101851Z is the 10th at 1851, not 1018 on some day.

In the contiguous 48 states the ICAO identifier is K plus the three-letter domestic identifier. Alaska starts with PA, Hawaii with PH, Canada with CU, CW, CY or CZ (AIM 7-1-29). If a report has a modifier, it sits next. AUTO means a fully automated report with no human oversight. COR means a correction sent to replace an earlier report, and it keeps the time of the report it corrects (FAA-H-8083-28B, 24.4.3.3 and 24.4.3.4). No modifier means an observer took the observation or augmented the automated one (AIM 7-1-29).

Wind is true, and it is not the wind on the radio

24012G20KT 200V280 is wind from 240 degrees true at 12 knots, gusting to 20, with the direction varying between 200 and 280. Direction is coded in tens of degrees relative to true north, averaged over two minutes (FAA-H-8083-28B, 24.4.3.5). A gust is appended with G only when the speed varies by 10 knots or more between peaks and lulls in the last 10 minutes. Calm is 00000KT.

The variability group appears only when the direction swings 60 degrees or more and the speed is above 6 knots (24.4.3.5.3). At 6 knots or less a wandering wind is coded VRB, as in VRB03KT. A speed of 100 knots or more takes three digits.

The trap is the reference. Everything on the national network, meaning the text METAR, FIS-B and the briefing, reports direction in true degrees. The same station's voice broadcast on the radio or telephone gives it in magnetic degrees (FAA-H-8083-28B, 24.3.1.2). The difference is the magnetic variation printed on your sectional. Convert before you compare the METAR wind to a runway, or listen to the ASOS instead. This one heads the most common METAR and TAF misreads.

Visibility and runway visual range

6SM is a prevailing visibility of 6 statute miles. Prevailing visibility is the greatest distance that can be seen throughout at least half of the horizon circle, not necessarily continuous (FAA-H-8083-28B, 24.4.3.6). Fractions get a space: 1 1/2SM. Automated stations report anything 10 miles or greater as 10SM, and less than a quarter mile as M1/4SM, M for minus (AIM 7-1-29; FAA-H-8083-28B, 24.4.3.6).

An RVR group such as R17L/2600FT appears only when the station has RVR equipment and the visibility is low: prevailing visibility of 1 SM or less, or RVR on the designated instrument runway of 6,000 feet or less (24.4.3.7). A V between two values means it varied, an M means below the lowest reportable value and a P means above the highest.

Weather codes are built from three columns

-RA BR is light rain and mist. A weather group is assembled from an intensity or proximity qualifier, an optional descriptor, and the phenomenon itself, in that order (FAA-H-8083-28B, Table 24-3). A report carries at most three weather groups.

The columns are from Table 24-3 of the Aviation Weather Handbook (FAA-H-8083-28B); the same table is on the back of the AIM 7-1-28 key.

The intensity sign belongs to the precipitation, not the obscuration, so -RA BR is light rain with mist, not light mist. When two kinds of precipitation share one group the intensity is not cumulative: -FZRAPL is light freezing rain and light ice pellets (24.4.3.8.1). The qualifier VC means the phenomenon is between 5 and 10 statute miles from the point of observation and never carries an intensity, so VCSH says showers are nearby without saying how heavy (24.4.3.8.2). Fog, FG, is reported when visibility is below 5/8 mile; mist, BR, covers 5/8 mile up to 6 miles (AIM 7-1-29). UP is an automated station admitting its sensor cannot tell what is falling.

Sky condition, and what counts as a ceiling

SCT012 BKN025 OVC060 is scattered at 1,200 feet, broken at 2,500 and overcast at 6,000. Each layer is a coverage contraction followed by the height of its base in hundreds of feet above ground level, listed in ascending order and ending at the first overcast layer (FAA-H-8083-28B, 24.4.3.9). Coverage is in eighths of the sky: FEW is 1/8 to 2/8, SCT is 3/8 to 4/8, BKN is 5/8 to 7/8 and OVC is 8/8 (Table 24-4). Heights are reported to the nearest 100 feet up to 5,000, the nearest 500 from 5,001 to 10,000, and the nearest 1,000 above that (Table 24-5), so OVC060 could be a base anywhere from about 5,750 to 6,250.

The ceiling in the example is 2,500 feet, the broken layer, not the scattered layer below it. Lowest broken or overcast wins. Under 14 CFR 1.1 a ceiling is the height above the surface of the lowest layer of clouds or obscuring phenomena reported as broken, overcast or obscuration, and not classified as thin or partial. FEW and SCT are never a ceiling, however low. VV followed by a height is an indefinite ceiling: the sky is totally obscured and the number is how far up you can see into it (24.4.3.9).

Clear skies come in two flavors. SKC is coded by a human observer who sees no layers at all. CLR is coded by an automated station and means no layers were detected at or below 12,000 feet (Table 24-4, note 1). An ASOS cannot see above 12,000, so CLR says nothing about a cirrus deck or a thunderstorm anvil overhead. US TAFs forecast clear sky as SKC, never CLR (AIM 7-1-28).

At manual stations CB or TCU is appended to a layer: SCT023TCU is scattered towering cumulus at 2,300 feet (24.4.3.9). Coverage is cumulative. Each layer is reported as the total sky cover at and below its height, which is why the handbook's Figure 24-4 codes 2/8 at 1,200 feet, 1/8 more at 3,000 and 2/8 more at 5,000 as FEW012 SCT030 BKN050.

Temperature, dew point and altimeter

18/16 A2985 is temperature 18 degrees Celsius, dew point 16, altimeter 29.85 inches of mercury. Both temperatures are whole degrees, rounded, and below-zero values take an M: 04/M02 is plus 4 and minus 2 (FAA-H-8083-28B, 24.4.3.10). A missing dew point leaves the temperature followed by a slash, as in 02/. No temperature, no group. The altimeter is A plus four digits with the decimal point removed, so 29.92 inches of mercury is coded A2992 (24.4.3.11). Outside the US it is hectopascals with a Q prefix, as in Q1013 (AIM 7-1-28). Set it first.

The remarks, decoded

RMK starts the remarks, which the handbook splits into two categories: automated, manual and plain language remarks, then additive and maintenance data (FAA-H-8083-28B, 24.4.3.12). They appear in a fixed order too (Table 24-6). The codes worth knowing:

• AO1 / AO2: type of automated station. AO2 has a precipitation discriminator that can tell rain from snow; AO1 does not (24.4.3.13.3).
• PK WND 25028/22: peak wind since the last METAR, 250 at 28 knots at 22 past the hour. Only the minutes appear when the hour is the report hour; a different hour gets four digits (24.4.3.13.4). The AIM adds that the remark appears whenever the peak exceeds 25 knots (AIM 7-1-29).
• LTG DSNT W: lightning detected 10 to 30 nautical miles west. Within 5 NM an automated station codes TS in the body; 5 to 10 NM is VCTS (24.4.3.13.10). Distances in remarks are statute miles except for automated lightning.
• RAB15: rain began at 15 past the hour. RAB05E30SNB20E55 is rain from 05 to 30 and snow from 20 to 55 (24.4.3.13.11). TSB0159E30 is a thunderstorm from 0159 to 0230.
• PRESFR / PRESRR: pressure falling or rising rapidly, coded when the rate is at least 0.06 inch per hour and the change totals 0.02 inch or more (24.4.3.13.21). PRESFR with a dropping altimeter is a reason to reset before an approach.
• SLP108: sea level pressure 1010.8 hectopascals. Only the tens, units and tenths are coded; you supply the leading 9 or 10, so SLP982 is 998.2 and SLP132 is 1013.2 (24.4.3.13.22). SLPNO means not available.
• P0004: four hundredths of an inch of liquid precipitation since the last METAR (AWC product reference, quoting FMH-1).
• T01780156: hourly temperature and dew point to tenths. T, then a sign digit (0 positive, 1 negative), then three digits, twice. 0178 is 17.8 degrees and 0156 is 15.6; T00261015 would be plus 2.6 and minus 1.5 (24.4.3.14.1).
• PWINO, TSNO, PNO, FZRANO, RVRNO: a sensor that should be reporting is not: present weather, lightning, rain gauge, freezing rain, RVR (24.4.3.14.2.1). A station reporting TSNO cannot tell you there is no thunderstorm.
• $: the automated system has detected that it needs maintenance (24.4.3.14.2.2).

Climatological groups such as 10178 20094, the 6-hourly maximum and minimum temperatures (AWC product reference), are marked in the handbook as having no direct impact on aviation (Table 24-6). Skip them.

Reports outside the US

The METAR code is an ICAO standard with national variations, and the AIM lists the US ones: statute miles for visibility, feet for RVR, knots for wind, inches of mercury for the altimeter (AIM 7-1-29). Elsewhere expect visibility as four digits in meters, RVR in meters and a Q altimeter (AIM 7-1-28). Wind may be in kilometers per hour or meters per second (FAA-H-8083-28B, 24.4.3.5).

CAVOK replaces the visibility, weather and sky groups when visibility is 10 km or more, there is no cloud below 5,000 feet or below the highest minimum sector altitude, whichever is greater, no cumulonimbus and no significant weather. The handbook defines it in the TAF chapter and notes that the NWS does not use it domestically (FAA-H-8083-28B, 27.4.2.6); a Paris or Rome METAR on a fine morning reads CAVOK in the same slot. The arithmetic for turning 4000 meters or 9999 into a flight category is in Flight categories explained.

What a METAR cannot tell you

A METAR is one point, one moment, through one set of sensors. An ASOS reports sky condition only up to 12,000 feet, and its clouds and visibility are time-averaged, 30 minutes for clouds and 10 minutes for visibility, with algorithms built to report deteriorating conditions faster than improving ones (FAA-H-8083-28B, 24.3.1). The voice broadcast on the field frequency is the one-minute observation and may not match the METAR on your screen. An AWOS generates a METAR every 20 minutes and does not issue SPECIs at all (24.3.2), so at an AWOS field the absence of a special report means nothing. Watch the 20-minute reports instead.

The codes announce the sensing limits if you read them: UP for precipitation of unknown type, CLR for nothing seen below 12,000, TSNO for a lightning detector that is down. Nothing in a METAR describes the route, the ridge between airports or the next three hours. That is the job of the TAF, the advisories and PIREPs.

FlyFren's free airport weather decoder takes any ICAO identifier and shows the current METAR and TAF from the NWS Aviation Weather Center, decoded group by group. It is supplemental information, not an official weather briefing. The AWC METAR page has the raw and decoded text for any US station, and the AWC product reference reproduces the FMH-1 remark definitions if you meet a code skipped here.

This article is educational and is not a substitute for the current regulations, the AIM, official weather briefings, or instruction from a CFI. Check the current text at the linked sources before you rely on any detail.