Decoding the METAR and the cryptic weather report that decides whether you fly today

A METAR is a standardized aviation weather observation issued every hour that encodes wind, visibility, clouds, temperature, dew point, and pressure into a single line of text. Learning to read it fluently is a core requirement for the private pilot checkride and, more importantly, for making safe go/no-go decisions every time you fly. This guide breaks down each section in order, using a real-world example, so you can glance at a METAR and see weather instead of alphabet soup.

What Does a METAR Look Like?

Here is a sample METAR for Chicago Midway (KMDW):

METAR KMDW 120953Z 35010KT 10SM FEW040 SCT070 BKN120 18/12 A2992 RMK AO2 SLP053

Every group of characters has a specific job, and they always appear in the same order. Once you learn the sequence, you know exactly where to look for the information you need.

What Do the Report Type and Station Identifier Tell You?

The word METAR at the beginning identifies this as a routine hourly observation, typically issued around 53 minutes past the hour. If you see SPECI instead, that is a special observation — conditions changed rapidly enough that controllers couldn’t wait for the next scheduled report. A SPECI demands extra attention because the weather is actively shifting.

KMDW is the station identifier. The K prefix indicates a station in the contiguous United States. MDW is Midway’s three-letter code. Every weather-reporting airport worldwide has a four-letter ICAO identifier.

How Do I Read the Date and Time Group?

120953Z breaks down as:

• 12 — the 12th day of the month
• 0953Z — 0953 Zulu (Coordinated Universal Time)

Aviation uses a single global clock to eliminate time zone confusion. To convert Zulu to local, subtract the offset for your time zone (for example, subtract 5 hours for Central Daylight Time).

The time group also tells you how old the report is. A METAR that is two hours old may no longer reflect current conditions. Always check the age. Stale weather is dangerous weather.

How Do I Decode the Wind Group?

35010KT means the wind is coming from 350 degrees (just west of due north) at 10 knots.

• The first three digits are the direction the wind blows from, referenced to true north.
• The next two or three digits are the speed in knots.

Variations you will encounter:

What Does the Visibility Number Mean?

10SM means 10 statute miles — the maximum reported value. Visibility could be 50 miles and the METAR still reads 10SM.

When visibility drops, you will see values like 5SM, 3SM, 1 1/2SM, or 1/4SM. The prefix M means “less than,” so M1/4SM means less than one-quarter statute mile — essentially fog. You are not flying VFR in that.

For VFR in Class G airspace during the day, you need at least 3 statute miles of visibility. If the METAR shows 2SM, the answer is already clear.

What Are the Weather Phenomenon Codes?

After visibility, the METAR reports what is happening in the atmosphere using standardized abbreviations:

Intensity prefixes modify these codes:

• -RA = light rain
• RA (no prefix) = moderate rain
• +TSRA = heavy thunderstorm with rain

A plus sign in front of TS should get your full attention. That is a hard no for VFR flight.

How Do I Read Cloud Layers and Find the Ceiling?

Cloud groups report coverage and height in hundreds of feet AGL (above ground level, not sea level).

FEW040 SCT070 BKN120

The numbers are altitude in hundreds of feet AGL: 040 = 4,000 ft, 070 = 7,000 ft, 120 = 12,000 ft.

The ceiling is the lowest BKN or OVC layer. In this example, the ceiling is broken at 12,000 feet — plenty of room for VFR. Few and scattered layers are not ceilings because you can see through them.

Two other codes to know: CLR (clear below 12,000 ft, reported by automated stations) and SKC (sky clear, reported by a human observer).

A common trap: seeing SCT008 and thinking “it’s only scattered, not a ceiling, so I can fly.” Technically correct — scattered is not a ceiling. But if half the sky at 800 feet AGL is covered with clouds, you need to ask whether maneuvering around those bases in a training airplane is a sound decision. The METAR gives you data. The judgment is yours.

Why Do Temperature and Dew Point Matter?

18/12 means a temperature of 18°C and a dew point of 12°C. Below-zero values get an M prefix (M02 = minus 2°C).

The temperature-dew point spread tells you how close the air is to saturation. When temperature and dew point converge, moisture condenses into clouds, fog, or reduced visibility.

• 6°C spread (as here): comfortable margin.
• 3°C or less: watch closely.
• 2°C or less: conditions can deteriorate fast, especially near sunrise when temperature drops.

Practical tip: If successive METARs show the spread narrowing through the afternoon or evening, expect visibility to worsen. Plan your return before conditions slip below VFR.

How Do I Use the Altimeter Setting?

A2992 means set your altimeter’s Kollsman window to 29.92 inches of mercury. This ensures your altitude reads correctly. A wrong setting makes your altimeter lie — quietly.

A one-hundredth of an inch error equals roughly 10 feet. Flying from high pressure to low pressure without updating the altimeter means you are lower than indicated. The rule of thumb: “High to low, look out below.”

29.92" is standard pressure — pressure altitude equals field elevation. Higher than standard means better aircraft performance; lower means worse. This ties directly into density altitude calculations for takeoff and landing.

What Is Hiding in the Remarks Section?

Everything after RMK is supplemental detail. In our example:

• AO2 — automated station with a precipitation discriminator (can distinguish rain from snow from freezing rain). AO1 stations lack this capability.
• SLP053 — sea level pressure of 1005.3 millibars.

Remarks can also include tower visibility, variable ceiling reports, thunderstorm movement, and pressure trends. For the private pilot checkride, know what AO1 vs. AO2 means and scan remarks for anything safety-critical.

International METARs may include NOSIG (no significant change expected) as a trend forecast. This is rare in the United States but may appear on cross-border flights into Canada.

Putting It All Together: Two Go/No-Go Scenarios

Scenario 1 — No-go: OVC009 2SM BR 18008KT 14/13

Ceiling 900 feet, visibility 2 miles, temp-dew point spread 1°C. This fails basic VFR minimums (1,000-foot ceiling, 3 miles visibility in most controlled airspace), and the tight spread suggests it is getting worse. The METAR is telling you no.

Scenario 2 — Go: 10SM FEW045 31006KT 24/10 A3005

10 miles visibility, few clouds at 4,500 feet, winds at 6 knots, 14°C dew point spread, high pressure. That is a beautiful day to fly.

The METAR gave you the same kind of answer both times. You just had to know how to read it.

How to Lock This In

Print out 10 random METARs from airports around the country. Decode each one from memory without references. Circle the parts that stump you, then go back and fill in the gaps. Repeat a few times and you will start reading METARs the way you read a sentence — not letter by letter, but all at once.

The Airman Certification Standards for the private pilot checkride expect you to decode METARs and use them for weather decisions. An examiner may hand you a METAR during the oral and ask, “Would you fly today?” They want to see that you understand what the weather is doing and whether it is safe — not that you can recite codes.

For deeper study, reference the FAA’s Aviation Weather Services advisory circular (AC 00-45H) and the Pilot’s Handbook of Aeronautical Knowledge, both available free on the FAA website.

Key Takeaways

• METARs follow a fixed order — report type, station, time, wind, visibility, weather, clouds, temp/dew point, altimeter, remarks — so you always know where to find each element.
• The ceiling is the lowest BKN or OVC layer, not scattered or few. But low scattered layers still demand good judgment.
• Temperature-dew point spread is your early warning system for fog and low visibility. Watch it tighten across successive reports.
• Always check the METAR’s age. An observation from two hours ago may not reflect current conditions.
• The altimeter setting keeps you at the right altitude. Update it en route, especially when flying from high to low pressure.