METAR decoder

Where a METAR comes from

How METAR groups work

A fixed sequence of groups

The groups always come in the same order: station, time, wind, visibility, weather, clouds, temperature and dewpoint, altimeter, then remarks. That order matters because a METAR uses no labels — each group is identified by its position, not by a prefix. A missing group (no weather phenomena, for example) is simply absent, and the groups around it close the gap. Once you recognize the sequence, you know what each group means by where it sits.

Wind

Direction in degrees, speed in knots, then KT. Gusts show up as G and the gust speed. If the wind is swinging, a second group gives the range (like 180V260). VRB means it has no steady direction.

Visibility and weather

US reports give visibility in statute miles (10SM, 1/2SM). Most of the world uses meters. Weather uses short codes: RA for rain, SN for snow, FG for fog, TS for thunderstorm. A minus means light, a plus means heavy. So +TSRA is a heavy thunderstorm with rain.

Runway Visual Range (RVR)

When visibility drops below one statute mile, many airports report the Runway Visual Range. The group starts with R, then the runway designator, a slash, and the visibility in feet. A V between two values shows a range. A trend follows the value: U for up, D for down, N for no change. RVR appears between the visibility and weather groups.

R28L/0600V1000FT

R RVR prefix28L runway0600V1000 visibility range (ft)

CAVOK

CAVOK replaces the visibility, weather and cloud groups when three conditions are met: visibility is 10 km or more, no cloud below 5,000 ft or below the highest minimum sector altitude (whichever is greater), and no significant weather. US METARs never use CAVOK. International reports use it routinely. When you see it, the conditions are better than anything a set of codes would describe.

Clouds and the ceiling

Each cloud layer says how much of the sky it covers (FEW, SCT, BKN, OVC) and its height in hundreds of feet above the ground. The ceiling is the lowest broken or overcast layer. Scattered layers below it do not count, even if they are low.

FEW1–2 oktas

SCT3–4 oktas

BKN5–7 oktas

OVC8 okta

Temperature, dewpoint, and altimeter

Temperature and dewpoint are whole degrees Celsius, joined by a slash. An M in front means below zero: M04 is minus 4. The altimeter setting comes last. A means inches of mercury (US), Q means hectopascals (most of the world).

Flight category

The METAR carries no category field — the tool computes it. The ceiling is the lowest broken (BKN) or overcast (OVC) layer, not the lowest cloud. Three scattered layers at 500 ft are not a ceiling, and the category stays VFR if visibility is good. The category is the worse of the two limits: a 5,000-ft ceiling with 2-mile visibility is IFR because the visibility alone puts it there.

Ceiling \ Visibility	< 1 SM	1–3 SM	3–5 SM	5+ SM
3,000+ ft	LIFR	IFR	MVFR	VFR
1,000–3,000 ft	LIFR	IFR	MVFR	MVFR
500–1,000 ft	LIFR	IFR	IFR	IFR
Below 500 ft	LIFR	LIFR	LIFR	LIFR

Remarks

Everything after RMK is free-form and varies by country: station type, sea level pressure, hourly precipitation, peak wind, and more. This tool shows the remark section as it arrived. Decoding only the known groups would silently drop the rest.

Worked example

Weather abbreviation reference

Weather codes have an optional intensity prefix and one or more phenomena codes. For example, +TSRA means heavy (+) thunderstorm (TS) with rain (RA).

Intensity prefixes

Descriptors

Descriptors modify the precipitation or obscuration that follows them. They always come before the phenomenon code.

Weather phenomena

Common US remarks

Everything after RMK is US-specific. These are the groups you will see most often in a domestic METAR.

US vs ICAO format differences

The METAR format is international, but the US and the rest of the world differ on units and conventions.