How to read a METAR

A METAR is a coded report of the weather actually observed at an aerodrome at a given time, and learning to read one straight off the page is a basic airmanship skill.

This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.

What a METAR is (and is not)

A METAR is an observation: it describes conditions that were measured, not predicted. That makes it different from a TAF, which is a forecast. When the weather changes significantly between routine reports, a special report called a SPECI is issued using the same code form.

The METAR code is an international standard. The requirement to provide it sits in ICAO Annex 3, and the exact code form is defined in the WMO Manual on Codes (WMO No. 306). Because it is standardised, the same groups appear in the same order whether you are reading a report from London, Lagos, or Los Angeles, with a few regional conventions noted below.

A worked example

Here is a typical European METAR:

METAR EGLL 181150Z 24012G22KT 9999 -RA FEW012 BKN025 11/09 Q1004 NOSIG

Reading it group by group:

• METAR is the report type. A routine report says METAR; an unscheduled special says SPECI.
• EGLL is the ICAO four-letter location indicator, here London Heathrow.
• 181150Z is the day and time: the 18th of the month at 1150 UTC. The Z stands for Zulu, which is UTC. This is the single most common beginner trap, so read it as UTC, never as local time.
• 24012G22KT is the wind: from 240 degrees at 12 knots, gusting 22 knots. VRB replaces the direction when the wind is variable, and a group such as 210V270 is added when the direction varies across a wide arc.
• 9999 is the visibility: 10 km or more. In the ICAO code, visibility is given in metres, so 0800 means 800 metres.
• -RA is the present weather: light rain. The intensity prefix is - for light, + for heavy, and nothing for moderate. Common descriptors include RA rain, SN snow, BR mist, FG fog, and TS thunderstorm.
• FEW012 BKN025 describes the cloud: few at 1200 ft and broken at 2500 ft. Cloud base heights are in hundreds of feet above the aerodrome.
• 11/09 is the air temperature (11 C) and dewpoint (9 C). A negative value carries the prefix M, so M02 means minus 2 C. The closer these two numbers are, the higher the humidity and the greater the risk of mist, fog, or icing.
• Q1004 is the pressure setting (QNH) of 1004 hectopascals.
• NOSIG is a trend that says no significant change is expected in the next two hours.

Try it yourself below. Paste a METAR into the decoder and it explains each group the same way. It only explains the text you enter; it does not fetch live weather.

Cloud amounts in oktas

Cloud cover is reported in oktas, or eighths of the sky. The abbreviations map to ranges set out by the UK Met Office and the FAA:

• FEW is few, 1 to 2 oktas.
• SCT is scattered, 3 to 4 oktas.
• BKN is broken, 5 to 7 oktas.
• OVC is overcast, 8 oktas.

A ceiling, for the purposes of approach minima, is generally the lowest broken or overcast layer.

CAVOK and the pressure trap

When conditions are good enough, the visibility, weather, and cloud groups are replaced by the single word CAVOK (ceiling and visibility OK). Per the Met Office, CAVOK means all three of these at once: visibility 10 km or more; no cloud below 5000 ft or below the highest minimum sector altitude, whichever is greater, and no cumulonimbus or towering cumulus at any height; and no weather significant to aviation.

The most useful EASA-versus-FAA contrast is the pressure group. The ICAO and EASA convention reports QNH in whole hectopascals with a leading Q, for example Q1013. The United States reports the altimeter setting in inches of mercury with a leading A, for example A2992, as the FAA AIM sets out. US METARs also report visibility in statute miles with an SM suffix (10SM) rather than in metres, and place extra automated data after the keyword RMK. Set the wrong units in the wrong region and your altimeter will be badly out.

Common pitfalls

• Time is UTC, not local. Convert deliberately.
• Wind direction is degrees true in the written report. The spoken winds you get from the tower or ATIS for take-off and landing are degrees magnetic, so the two can differ by the local variation.
• Cloud heights are above the aerodrome, not above mean sea level.
• Watch the units by region: metres and hectopascals in the ICAO form, statute miles and inches of mercury in the US form.

In Pilot EFB

Pilot EFB shows the decoded METAR alongside the raw text, and the raw report is always kept, never replaced, so you can check the plain-language decode against the original groups. A briefing you have already pulled stays readable with no signal, because your device is the source of truth for what you have saved. Pulling a fresh observation needs a connection. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.