The METAR Decoded - Every Group in Order and What Your Airport Is Actually Telling You

A METAR is a standardized airport weather observation issued once an hour, and it follows a fixed sequence of groups that pilots and controllers worldwide can read in about 30 seconds once the structure is familiar. The code looks opaque at first, but each group answers a specific operational question - current wind, visibility, ceiling, temperature spread, altimeter setting - in a defined order every time. Understanding that structure turns a string of letters and numbers into a clear picture of what your airport is actually doing right now.

What Does a Real-World METAR Look Like?

Working through a complete example is the fastest way to internalize the format. Here is a representative observation from Chicago Midway (KMDW):

METAR KMDW 121755Z 27015G25KT 3/4SM +TSRA BR BKN020CB OVC040 18/16 A2979 RMK AO2 TSB10 SLP091 P0015

This is a summer afternoon observation with nearly every significant weather element present - gusting wind, low visibility, thunderstorm, a cumulonimbus ceiling, and a tight temperature-dew point spread. Every group below maps directly to this example.

What Does the Report Type Tell You?

The first element is either METAR or SPECI.

A routine METAR publishes once per hour, typically at 55 minutes past. A SPECI is a special observation issued between scheduled reports when conditions change rapidly or cross significant thresholds - visibility drops below 3 miles, ceiling drops below 1,000 feet, or a thunderstorm begins or ends.

If you see SPECI, conditions just changed. Read it.

How Do You Read the Station Identifier?

The four-letter ICAO code identifies the reporting airport. In the United States, most identifiers begin with K - KMDW is Midway, KATL is Atlanta, KORD is O’Hare. Canadian airports begin with C; Mexican airports begin with M.

The identifier also carries a critical operational reminder: that observation is a point measurement. It tells you what conditions looked like at that specific location at that specific moment. Conditions two miles away can be dramatically different. Building a preflight weather picture requires combining multiple observations across the entire route, not just the departure airport.

What Does the Date and Time Group Mean?

121755Z reads as the 12th day of the month at 1755 Coordinated Universal Time (Zulu). Every METAR is time-stamped in Zulu regardless of local time zone. In Central Daylight Time, 1755Z is 12:55 PM local.

Aviation weather runs on Zulu. Get comfortable converting before you need to do it quickly.

How Do You Read the Wind Group?

27015G25KT breaks into three parts: direction, speed, and gust speed.

Direction is in magnetic degrees rounded to the nearest 10 degrees. 270 means the wind is from the west - from 270°. That determines your runway selection before you even call ground.

Speed is in knots. Here it is 15 knots, gusting to 25 knots. When gusts are present, you see G followed by the gust value. A practical technique for approach speed in gusty conditions: add half the gust spread to your normal approach speed. Here the spread is 10 knots, so add 5 knots to Vref and be ready for the wind to die right at the threshold.

Variable winds are coded VRB followed by speed. If the wind direction swings more than 60 degrees, the variable sector is written out (example: 250V310). That is a crosswind that will not hold still - calculate your crosswind component against your aircraft’s demonstrated crosswind limit.

How Do You Read Visibility?

3/4SM means three-quarters of a statute mile. United States METARs report visibility in statute miles, not nautical miles - know that distinction before your checkride.

Three-quarters of a mile is well below VFR minimums. Class D, E, and controlled Class G airspace above 1,200 feet AGL require 3 statute miles visibility for VFR. Class G below 1,200 feet AGL during the day drops to 1 statute mile, but 3/4SM does not satisfy even that standard. This observation is not VFR anywhere.

On a checkride oral, the visibility group is usually where the examiner starts the conversation.

What Does the Present Weather Group Tell You?

This is a two-part system: intensity modifier plus phenomenon.

A plus sign means heavy. A minus sign means light. No symbol means moderate. Descriptors include TS (thunderstorm), SH (showers), FZ (freezing), BL (blowing). Phenomena include RA (rain), SN (snow), FG (fog), BR (mist), HZ (haze), GR (hail).

The Midway example shows +TSRA BR - heavy thunderstorm rain and mist. The BR code (mist) applies when visibility is between 5/8 and 6 miles with high relative humidity. FG (fog) applies when visibility drops below 5/8 of a mile under similar conditions.

On thunderstorms specifically: TS in the present weather group means the storm is at or within 10 nautical miles of the airport. Not down the road. Not on radar 50 miles away. Within 10 miles of the field. That is not a situation to launch into.

How Do You Find Your Ceiling in the Sky Condition Group?

The sky condition group is where your ceiling lives.

SKC means sky clear. CLR means no clouds detected below 12,000 feet, typically used by automated stations. Cloud layers are coded with coverage and height: FEW (1–2 eighths), SCT (3–4 eighths), BKN (5–7 eighths), OVC (8 eighths / complete coverage). The number after each code is the cloud base in hundreds of feet AGL - BKN020 means broken at 2,000 feet above the airport surface.

Your ceiling for VFR purposes is the lowest broken or overcast layer. Few and scattered layers do not define a ceiling. In the Midway example, BKN020 is the ceiling at 2,000 feet. Basic VFR in Class D and E requires 1,000 feet ceiling and 3 miles visibility. This report has the ceiling - barely - but fails on visibility.

The CB suffix changes everything. BKN020CB means that broken layer contains cumulonimbus. This is not a low ceiling to scud-run under. This is the anvil of an active thunderstorm overhead. The observer added those two letters because they completely change the operational picture. TCU (towering cumulus) carries the same urgency - the storm is building and has not yet reached full cumulonimbus development. It will.

What Do Temperature and Dew Point Tell You?

18/16 means temperature 18°C, dew point 16°C. The spread is 2 degrees.

When temperature and dew point converge, relative humidity is high and the atmosphere is primed for fog, low ceilings, and precipitation. A useful field rule: the dew point spread closes at roughly 2 to 2.5°C per 1,000 feet of altitude. With a 2-degree spread at the surface, cloud bases will form very close to the ground - consistent with the 2,000-foot broken layer in this report.

On days when temperatures are near freezing and precipitation is present, check the temperature group for structural icing risk. FZra (freezing rain) and FZdz (freezing drizzle) in the present weather group combined with temperatures at or below 0°C represent serious hazards for unprotected airframes.

How Do You Set and Interpret the Altimeter?

A2979 means 29.79 inches of mercury. Set that in your Kollsman window whenever you are within 100 nautical miles of the reporting station below 18,000 feet.

Low altimeter readings correlate with low-pressure systems - a summer thunderstorm complex will pull surface pressure down. High readings correlate with high pressure and generally more stable air. The critical hazard: flying from a high-pressure area into a low-pressure area without updating your altimeter causes your indicated altitude to read higher than your true altitude. The memory aid is “from high to low, look out below.” Update your altimeter continuously along the route.

What Is in the Remarks Section - and Why Does It Matter?

RMK is simply the marker that remarks follow. A lot of pilots stop reading at the altimeter. The remarks section often contains the most operationally significant information in the entire report.

AO2 means the station has a precipitation discriminator and can distinguish rain from snow. AO1 means it cannot - in winter conditions, the precipitation type at an AO1 station is uncertain.

TSB followed by a time means thunderstorm began. TSB10 in this example means the storm started at 10 minutes past the hour. Combined with the observation time, that tells you roughly how long the storm has been sitting over the field.

SLP is sea level pressure in hectopascals, used for pressure analysis. P followed by four digits is precipitation since the last hourly observation in hundredths of an inch - P0015 means 0.15 inches of rainfall in the past hour.

Lightning entries - LTGCG (cloud to ground), LTGIC (cloud to cloud) - appear in the remarks with frequency descriptors: FRQ (frequent) and OCNL (occasional). OCNL LTGCG means lightning is reaching the ground near the field. That is not ambiguous.

RVR (Runway Visual Range) appears in very low visibility conditions. It reads as R followed by runway designation followed by visibility in feet - R28L/2400FT means Runway 28 Left has a runway visual range of 2,400 feet. Category I ILS approaches require at least 1,800 feet RVR. Category II approaches push that down to 1,200 feet. Know those numbers before flying actual IMC.

How Does the METAR Fit Into a Full Preflight Weather Briefing?

The METAR answers one question: what is it right now? It is one layer of a complete briefing, not the whole thing.

The TAF (Terminal Aerodrome Forecast) tells you what conditions should look like over the next 24 hours. AIRMETs and SIGMETs identify hazards along the route. PIREPs tell you what pilots who just flew through that airspace actually found. Winds aloft forecasts describe what cruise altitude air is doing. Each product answers a different question. If the current METAR already shows conditions below your minimums, the TAF does not save you - the flight does not happen today.

On a private pilot checkride oral, the examiner may hand you a briefing package and ask you to assess it for a planned departure. The answer is a chain of decisions - ceiling here, visibility there, potential icing at cruise altitude, convective activity in the area - not just a single number. The examiner is evaluating how you integrate information, not just whether you can locate the ceiling group.

Practice reading METARs every day, even when not flying. Pull up your home airport each morning. Pull a few along a route you would like to fly someday. The decoding becomes automatic quickly, and when you are actual IMC running a hold and trying to get an approach clearance, you need to be flying the airplane - not translating codes.

Key Takeaways

• A METAR follows a fixed group sequence: report type, station, date/time, wind, visibility, present weather, sky condition, temperature/dew point, altimeter, remarks - in that order, every time.
• Your ceiling is the lowest BKN or OVC layer. FEW and SCT layers do not define a ceiling for VFR purposes.
• TS in the present weather group means the thunderstorm is within 10 nautical miles of the field - not a distant radar return.
• A CB or TCU suffix on a sky condition group indicates an active or developing thunderstorm cell at that layer; it fundamentally changes the operational picture.
• The remarks section contains time-sensitive trend information - storm onset times, lightning type and frequency, precipitation totals, and RVR - that is not in the coded body of the report.
• The METAR is one product in a complete briefing. Cross-reference with TAFs, AIRMETs/SIGMETs, PIREPs, and winds aloft before making a go or no-go decision.