How To Decode a METAR: A Field-by-Field Weather Code Breakdown

By John Reed · May 14, 2026

Understanding how to decode a METAR is an essential skill for pilots, student aviators, flight dispatchers, and anyone who needs to interpret real-time aviation weather. A METAR is a dense string of codes and abbreviations, but once you know what each field represents, reading one becomes fast and intuitive. This guide walks through every component of a METAR report from start to finish, using a real example decoded field by field.

What Is a METAR?

METAR stands for Meteorological Aerodrome Report. It is a standardized format for reporting surface weather observations at airports and aerodromes around the world. The format is governed by two international bodies: the International Civil Aviation Organization (ICAO) and the World Meteorological Organization (WMO). Because those standards are global, a pilot in Tokyo can read a METAR from London or Chicago using the same knowledge.

METARs are issued on a routine schedule — typically every 30 or 60 minutes depending on the airport. When conditions change significantly between scheduled observations — for example, if visibility suddenly drops or a thunderstorm moves overhead — a SPECI (Special METAR) is issued immediately outside the normal cycle. SPECIs use the same format as routine METARs; only the report type identifier changes.

Pilots use METARs primarily for pre-flight planning to determine whether weather at the departure airport, en route, or at the destination meets the minimums required for their type of flight. Air traffic controllers also monitor METARs to communicate current conditions to arriving and departing aircraft.

Reading a METAR Line by Line

The best way to understand the METAR format is to take a real example and decode it one field at a time. Here is the example we will use throughout this guide:

At first glance this looks like a random sequence of characters. Let’s work through each field from left to right.

Field 1: METAR — Report Type

The first token identifies the type of report. METAR indicates this is a routine scheduled observation. If it were a special observation triggered by a significant weather change, this field would read SPECI. If a correction is being issued to fix an error in a previously transmitted report, the token COR appears here (e.g., METAR COR KSFO ...).

Field 2: KSFO — Station Identifier

KSFO is the ICAO 4-letter airport identifier for San Francisco International Airport. ICAO codes are assigned to every airport worldwide and always consist of four letters. The first letter or letters indicate the region:

• K — contiguous United States (e.g., KJFK, KORD, KLAX)
• C — Canada (e.g., CYYZ for Toronto Pearson)
• EG — United Kingdom (e.g., EGLL for London Heathrow)
• LF — France, ED — Germany, and so on across Europe
• RJ — Japan, ZB — northern China

Knowing the station identifier, you can look up the airport location to understand the geographic context of the observation.

Field 3: 121755Z — Date and Time

121755Z encodes when the observation was taken. The format is DDHHmmZ:

• 12 — the 12th day of the current month
• 17 — 17th hour (5 p.m.)
• 55 — 55th minute
• Z — Zulu time, meaning UTC (Coordinated Universal Time)

All METARs worldwide use UTC, not local time. This eliminates any ambiguity when sharing weather data across time zones. Pilots planning a cross-country or international flight always work in UTC, so METAR times integrate seamlessly with other aviation charts and NOTAMs.

Field 4: 28015KT — Wind

28015KT describes the surface wind. The format is dddffKT where:

• 280 — wind direction in degrees true (from the north, measured clockwise). Here, wind is coming from the west-southwest.
• 15 — wind speed in knots
• KT — unit is knots

A few important variations you will encounter:

• VRB replaces the direction when the wind is variable with no consistent heading — e.g., VRB05KT means variable at 5 knots.
• G indicates gusts. 28015G22KT means the wind is from 280° at 15 knots with gusts to 22 knots.
• Some stations report in MPS (meters per second) rather than knots, particularly outside the US.
• 00000KT means calm wind.

Field 5: 10SM — Visibility

10SM means visibility is 10 statute miles. The SM suffix denotes statute miles, used in US METARs. International METARs report visibility in meters. The value 9999 is used internationally to indicate visibility of 10 km or more — the maximum reportable value.

Other common US visibility values include 3SM (3 statute miles), 1/2SM (half a mile), and M1/4SM (less than one-quarter mile). Low visibility directly affects instrument flight rules (IFR) minimums and approach categories, making this one of the most operationally critical fields in the METAR.

Field 6: FEW040 — Sky Condition

FEW040 describes cloud coverage and height. The first three letters are the coverage code and the three digits after are the cloud base height in hundreds of feet above ground level (AGL). So FEW040 means a few clouds at 4,000 feet AGL.

Sky condition codes are covered in detail in the next section.

Field 7: 15/07 — Temperature and Dew Point

15/07 reports temperature and dew point separated by a slash, both in degrees Celsius — always Celsius, worldwide, regardless of local convention. Here, the temperature is 15°C and the dew point is 7°C.

Sub-zero values use the letter M (for minus) as a prefix. For example, M03/M08means temperature −3°C, dew point −8°C.

The spread between temperature and dew point is useful for estimating the likelihood of fog (a narrow spread, such as 2°C or less, increases fog probability) and for calculating cloud base heights for convective activity.

Field 8: A2992 — Altimeter Setting

A2992 is the altimeter setting— the sea-level pressure used to calibrate an aircraft’s altimeter.

• The A prefix means the value is in inches of mercury (inHg), used in the United States, Canada, and a few other countries. A2992 = 29.92 inHg.
• The Q prefix means the value is QNH in hectopascals (hPa), used internationally. Q1013 = 1013 hPa.

Standard sea-level pressure is 29.92 inHg (1013.25 hPa). Altimeter settings above or below standard affect how aircraft altimeters read, which is why pilots are required to update the setting whenever ATC provides a new altimeter or when switching between regional pressure areas.

Field 9: RMK AO2 — Remarks

RMK signals the start of the remarks section, which contains supplemental information primarily used in the United States. Everything after RMK is US-specific and follows its own set of conventions. In this example, AO2 indicates the station is an automated observing system equipped with a precipitation discriminator sensor.

The remarks section is covered in full detail further below.

METAR Sky Condition Codes Explained

Cloud coverage in a METAR is reported in oktas — eighths of the sky. Each coverage code maps to a range of oktas:

The three-digit number following the coverage code is the cloud base height in hundreds of feet AGL. So BKN025 means a broken ceiling at 2,500 feet AGL, and OVC008 means overcast at 800 feet AGL — a low ceiling that would likely require an instrument approach.

A METAR can report up to three separate cloud layers. Each layer is listed in ascending order of height. For example: FEW015 SCT060 BKN120 describes a few clouds at 1,500 ft, scattered at 6,000 ft, and a broken ceiling at 12,000 ft.

Two special cloud type suffixes can appear after the height:

• CB (Cumulonimbus) — a thunderstorm cloud. Operationally significant because it indicates severe turbulence, icing, and lightning potential. Example: FEW030CB
• TCU (Towering Cumulus) — a rapidly growing cumulus cloud that may develop into a cumulonimbus. Example: SCT025TCU

Weather Phenomena Codes

Present weather is reported between the visibility field and the sky condition field when significant precipitation or other phenomena are occurring. The weather code uses a structured system of prefixes, descriptors, and phenomena codes.

Intensity Prefixes

• - (minus/hyphen) — Light intensity. Example: -RA = light rain
• (no prefix) — Moderate intensity. Example: RA = moderate rain
• + (plus) — Heavy intensity. Example: +RA = heavy rain
• VC — In the vicinity (within 5–10 SM of the airport but not at the station). Example: VCTS = thunderstorm in the vicinity

Common Precipitation and Obstruction Codes

Descriptor Codes

Descriptors are two-letter qualifiers placed between the intensity prefix and the phenomenon code:

• TS — Thunderstorm (e.g., TSRA = thunderstorm with rain)
• SH — Shower (e.g., SHRA = rain shower, -SHSN = light snow shower)
• FZ — Freezing (e.g., FZRA = freezing rain, FZDZ = freezing drizzle)
• BL — Blowing (e.g., BLSN = blowing snow)
• DR — Low drifting (e.g., DRSN = low-drifting snow)
• MI — Shallow (e.g., MIFG = shallow fog)
• BC — Patches (e.g., BCFG = patchy fog)
• PR — Partial (e.g., PRFG = partial fog)

Weather codes can combine. +TSGR means heavy thunderstorm with hail. -FZDZ means light freezing drizzle. RASN means moderate rain and snow falling simultaneously.

Understanding the Remarks Section

The remarks section begins after the RMK token. It is primarily used in the United States and contains additional automated sensor data, supplemental weather information, and station metadata. International METARs generally do not include a remarks section.

Station Type

• AO1 — Automated station without a precipitation discriminator. The station can detect that precipitation is occurring but cannot distinguish between liquid and frozen precipitation types.
• AO2 — Automated station with a precipitation discriminator. The station can determine whether precipitation is rain, drizzle, snow, and so on.
• AUTO — Fully automated report with no human observer on site. This token appears in the body of the METAR (before the RMK section) when the observation was taken entirely by automated sensors.

Sea Level Pressure

SLP followed by three digits provides sea level pressure in hectopascals, with an implied leading digit. For example, SLP013 decodes as 1001.3 hPa (if the result would be below 1050, prepend 10; if it would be 1050 or above, prepend 9). SLP992 = 999.2 hPa.

Precipitation Accumulation

P followed by four digits reports precipitation accumulation in hundredths of an inch during the past hour. P0023 = 0.23 inches of precipitation. P0000 indicates a trace amount too small to measure.

Temperature in Tenths of a Degree

The body of the METAR reports temperature rounded to whole degrees Celsius. The remarks section can include a more precise reading in tenths. The format is T followed by eight digits: four for temperature and four for dew point, where a leading 1 indicates a negative value. T01500072 means temperature 15.0°C, dew point 7.2°C. T10280033means temperature −2.8°C, dew point 3.3°C.

Wind Shift and Peak Wind

WSHFT followed by a time indicates when a wind shift occurred. WSHFT 1735 means the wind shifted at 1735Z this hour.

PK WND reports the peak wind observed since the last METAR. PK WND 31045/1732 means peak wind from 310° at 45 knots, occurring at 1732Z.

Lightning and Thunderstorm Activity

Lightning observations are reported with direction and distance. For example, LTG DSNT W means lightning observed at a distance to the west. OCNL LTGICCG OHD means occasional lightning both in-cloud and cloud-to-ground overhead.

Corrections

When a previously issued METAR contained an error, a corrected version is transmitted with COR immediately after the report type. The corrected METAR replaces the erroneous one in its entirety.

Common METAR Abbreviations Quick Reference

The following table summarizes the most frequently encountered METAR abbreviations across all sections of the report.

Free Tools to Decode a METAR Automatically

While understanding the raw METAR format is valuable, several free online tools can parse a METAR into plain English instantly. These are useful for double-checking your manual interpretation or for quickly reading an unfamiliar report.

aviationweather.gov (NOAA)

The Aviation Weather Center, operated by NOAA, provides official US METARs at aviationweather.gov. The site displays both the raw METAR string and a decoded breakdown. You can search by airport identifier or by geographic region. All data comes directly from the National Weather Service and is considered authoritative for US operations.

CheckWX

checkwx.com offers a clean, color-coded METAR display that also includes TAFs (Terminal Aerodrome Forecasts) and PIREPs (pilot reports). It provides flight category coloring — VFR (green), MVFR (blue), IFR (red), and LIFR (magenta) — which makes it easy to assess conditions at a glance. CheckWX covers airports worldwide and is popular with both student pilots and professionals.

ForeFlight and Other EFBs

Electronic flight bag (EFB) applications such as ForeFlight, Garmin Pilot, and FltPlan Go all include integrated METAR displays with decoded views. These are the primary tools used by working pilots, as they integrate METARs with charts, TFRs, SIGMETs, and route planning.

ATIS and ASOS/AWOS Broadcasts

At towered airports, the current weather is broadcast on an ATIS (Automatic Terminal Information Service) frequency. ATIS reads out the current METAR in spoken form, updated each hour. At non-towered airports, an ASOS (Automated Surface Observing System) or AWOS (Automated Weather Observing System) broadcasts current conditions on a dedicated frequency, typically listed on sectional charts and in the Chart Supplement.