The METAR, the Raw Aviation Weather Report Every Student Reads Wrong, and the Decoded Observation That Tells You More Than Any App on Your Phone

A METAR - Meteorological Aerodrome Report - is a standardized weather observation recorded at a specific airport at a specific time, coded in a format every pilot must read without translation. Apps convert it to plain language, but your oral examiner will slide the raw coded version across the table and expect a confident, accurate reading. Learning to decode each field in sequence is the fastest way to close that gap.

What Is a METAR and When Is It Issued?

METAR stands for Meteorological Aerodrome Report. The acronym derives from French, which is why it does not map neatly onto English letters. Most airports equipped with an Automated Surface Observation System (ASOS) generate one every hour at 55 minutes past the hour. Airports with human observers typically issue at the top of the hour.

When conditions change significantly between scheduled observations - visibility drops, a new ceiling forms, a thunderstorm begins or ends - the system issues a SPECI, or special observation. A SPECI means conditions have shifted abruptly, and any METAR you read before it may no longer reflect current conditions at that field. When you are on approach in marginal conditions, the timestamp on your weather data matters.

How Do You Read the Station Identifier and Date-Time Group?

The first element is the station identifier. KBOS is Boston Logan International. All airports in the lower 48 contiguous states use a four-letter ICAO identifier beginning with K. Alaska uses the prefix PA, Hawaii uses PH, and Canadian airports begin with C. The identifier anchors the report to a specific location.

The date-time group follows immediately. In 121756Z, the first two digits - 12 - are the day of the month. The last four digits - 1756 - are the time in Coordinated Universal Time (UTC), also called Zulu time. The trailing Z confirms the time zone. Convert to local for personal situational awareness, but train yourself to read Zulu directly - it eliminates ambiguity.

AUTO in the type field means the observation was generated by automated equipment with no human oversight. Most small general aviation airports are automated. COR means the previous observation contained an error and this is the corrected version.

How Do You Read Wind in a METAR?

Wind is coded as direction and speed. 24012KT means the wind is from 240 degrees magnetic - roughly from the southwest - at 12 knots. When gusts are present, a G appears between sustained and peak: 24012G23KT means 12 knots sustained, gusting to 23 knots.

When gusts are reported, calculate your crosswind component for both the sustained wind and the peak gust. Plan your approach for the gust value. That is what the examiner expects to hear.

VRB before the speed indicates variable direction: VRB04KT is variable at 4 knots. Calm winds are coded as 00000KT. Calm can also be a signal to watch for convective heating as the day progresses.

How Do You Read Visibility in a METAR?

Visibility is reported in statute miles. 10SM means 10 statute miles. P6SM means visibility exceeds 6 statute miles but the sensor cannot measure further.

VFR minimums vary by airspace. In Class G airspace below 1,200 feet AGL, you need 1 statute mile and clear of clouds. Requirements increase in Class E and controlled airspace. When visibility drops, you will see fractions such as 3/4SM or 1 1/4SM. When that number approaches one mile, the sky condition and present weather fields will tell you why.

How Do You Decode Present Weather?

The present weather field has three components: intensity, descriptor, and phenomenon. If the field is empty, there is no precipitation or obscuration at the time of observation.

Intensity is coded with symbols: – (minus) means light, + (plus) means heavy, and no symbol means moderate. Common descriptors include TS (thunderstorm), SH (shower), FZ (freezing), and MI (shallow). Common phenomena include RA (rain), SN (snow), DZ (drizzle), FG (fog), BR (mist), and HZ (haze).

–RA is light rain. +TSRA is heavy thunderstorm with rain. FZRA is freezing rain - if your aircraft is not certified for known icing conditions and you see FZRA in the weather product for your destination, do not go. That is not a gray area.

FG combined with visibility below 1/4 statute mile represents the most restrictive conditions a VFR pilot will encounter. VCTS means thunderstorm in the vicinity, defined as between 5 and 10 statute miles from the observation point - close enough to influence your decision even if the storm is not directly overhead.

One important limitation of automated stations: the ASOS sensor only detects precipitation directly at the station. A convective cell two miles east of the field may be producing heavy rain without registering in the present weather field. That is why the remarks section carries extra weight at automated airports, and why a human observer at a tower-controlled field adds a layer of information the machine cannot provide.

How Do You Read Sky Condition and Identify a Ceiling?

Sky condition is one of the most critical fields. Each layer reports coverage and height. Heights in a METAR are always above ground level (AGL), not mean sea level (MSL) - a distinction that matters especially at high-elevation airports.

A ceiling is the lowest broken or overcast layer. Few and scattered layers are not ceilings. For VFR, you need a ceiling of at least 1,000 feet. In the Boston observation - FEW025 SCT060 BKN120 - the ceiling is 12,000 feet broken. Clear for all practical purposes.

A common student error is calling a scattered layer a ceiling. If you have FEW010 and SCT020 with nothing above, you have no ceiling - clouds to avoid, but you remain legal VFR provided visibility is adequate. The examiner will test this distinction.

If a sky condition layer ends with CB (cumulonimbus) or TCU (towering cumulus), the picture changes immediately. A CB tag means storm-producing clouds are present. FEW025CB could mean isolated thunderstorm cells in the area even if skies are otherwise relatively open.

How Do You Interpret Temperature and Dewpoint?

Temperature and dewpoint are reported in degrees Celsius, separated by a slash. 22/14 means temperature 22°C, dewpoint 14°C. A spread of 2°C or less indicates high relative humidity. As temperatures drop overnight toward the dewpoint, the two values converge - when they meet, relative humidity reaches 100% and fog forms.

Temperature also feeds directly into density altitude. The hotter and higher you are, the worse your aircraft performs. A high temperature reading in the METAR at a high-elevation airport on a warm day should immediately prompt a density altitude check before calculating takeoff performance.

How Do You Set the Altimeter From a METAR?

The altimeter setting is in inches of mercury. A3002 means 30.02 inHg. Set that in your Kollsman window and your altimeter will read field elevation on the ground, assuming the value has not drifted since you last updated it.

The rule of thumb: a 1-inch Hg difference between your set altimeter and the actual current setting produces approximately 1,000 feet of altitude error. The FAA requires pilots to update their altimeter to the nearest available reporting station along the route - on a long cross-country, that matters.

What Does the Remarks Section Tell You?

The remarks section - marked by RMK - is where most students lose information. It often contains the most operationally significant data in the entire report.

AO1 vs. AO2: An AO2 station has a precipitation discriminator and can distinguish between liquid and frozen precipitation. An AO1 station cannot. At an AO1 station, treat rain versus snow identification in the present weather field with extra caution.

SLP followed by three digits is sea level pressure in hectopascals. SLP167 becomes 1016.7 hPa. Use this to compare pressure patterns across stations and assess whether a low or high pressure system is nearby.

PRESRR means pressure rising rapidly. PRESFR means pressure falling rapidly. Falling rapidly signals an approaching low-pressure system moving faster than the hourly METARs may show. If you see PRESFR and are on the fence about a flight, weight that toward no-go.

PK WND shows the peak gust during the observation hour, including direction, speed, and the time it was recorded. If the peak is significantly higher than the wind in the main body, the wind spiked and came back down - the environment was not steady during that hour.

LTG DSNT ALL QUADS means lightning distant in all four quadrants. Even with a clean present weather field, that phrase means thunderstorm activity is surrounding the airport. TS B followed by two digits marks when the thunderstorm began; RA B followed by two digits marks when rain began. These are trend markers that show how recently conditions shifted.

How Do You Apply METAR Reading to a Real Go/No-Go Decision?

The examiner is not looking for definitions. The Airman Certification Standards (ACS) for the private pilot certificate require you to read a weather observation and produce a decision: what were conditions at that airport at that time, what do they mean for the planned flight, and what is the call.

Here are two complete observations that show how the full picture comes together.

Boston Logan (KBOS) - ordinary conditions:

KBOS 121756Z 24012KT 10SM FEW025 SCT060 BKN120 22/14 A3002 RMK AO2 SLP167 T02220144

Wind from 240° at 12 knots. Ten miles visibility. No precipitation. Ceiling at 12,000 feet broken. Temperature 22°C, dewpoint 14°C - a comfortable spread. Altimeter 30.02. This is a go. The observation is benign.

Chicago O’Hare (KORD) - no-go conditions:

KORD 121554Z 27015G28KT 3/4SM -TSRA BR BKN025CB OVC050 23/21 A2988 RMK AO2 PK WND 27032/1532 LTG DSNT ALL QUADS TS B10 RA B15 SLP116 P0004

Wind 270° at 15 knots, gusting 28. Visibility 3/4 statute mile. Active thunderstorm with rain and mist. Ceiling 2,500 feet broken, cumulonimbus. Overcast at 5,000 feet. Temperature 23°C, dewpoint 21°C - a 2-degree spread. Altimeter 29.88 inHg, well below the standard of 29.92, confirming a low-pressure system. Remarks: peak gust 32 knots at 1532Z, lightning in all quadrants, thunderstorm began 10 minutes before observation, rain began at 15 past, 0.04 inches of rain in the last hour.

No-go. Under any circumstances, for any light aircraft without an instrument rating and appropriate equipment. A trained pilot should be able to read that picture in under a minute.

How Should You Build METAR Reading Fluency Before the Checkride?

Pull the raw METARs for two or three nearby airports on the NOAA Aviation Weather Center website every morning before opening any app. Decode them out loud, the way you will have to on the oral. Then check the app translation. The gap closes fast. After a few weeks, raw METAR code reads like plain English - and on checkride day, that sheet of paper will not rattle you.

Key Takeaways

• A METAR is a standardized hourly airport weather observation; a SPECI is issued when conditions change significantly between scheduled observations - treat it as the most current picture available.
• Heights in a METAR are always AGL, not MSL - this distinction matters especially at high-elevation airports.
• A ceiling is the lowest broken or overcast layer; few and scattered layers do not form a ceiling, and confusing them is one of the most common student errors.
• The remarks section (RMK) frequently contains the most operationally significant information in the report, including peak gusts, pressure trends, and lightning activity that the main body may not reflect.
• A temperature/dewpoint spread of 2°C or less signals high relative humidity and potential fog formation - especially overnight as temperatures fall toward the dewpoint.