How to Read an Aviation METAR — A Pilot-Friendly Breakdown

Learning to read a METAR has gotten complicated with all the conflicting guidance flying around — decoder tools that assume you already speak the language, FAA documents the size of a small novel, laminated reference cards that dissolve in a sweaty kneeboard pocket somewhere over central Ohio. I went through three of those cards before my private pilot checkride. None of them made it. This is the guide I actually wanted back then — the one that treats you like someone who needs the logic explained, not just the codes listed.

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METAR in 60 Seconds

Here’s a real METAR. Let’s pull it apart before we go any deeper.

METAR KBOS 121554Z 27018KT 10SM FEW045 BKN090 22/14 A2992 RMK AO2 SLP132 T02220139

That string of characters tells you nearly everything you need for a go/no-go decision. Once you know the format — and it never changes — you can decode any US METAR in under 30 seconds. Here’s what each chunk means, left to right:

• METAR — Report type. Routine observation. (SPECI means special, unscheduled — more on that later.)
• KBOS — ICAO station identifier. K prefix means US airport. Boston Logan in this case.
• 121554Z — Date and time. The 12th of the month, at 1554 UTC (Zulu). Always UTC. Always.
• 27018KT — Wind. From 270° (due west) at 18 knots.
• 10SM — Visibility. 10 statute miles. That’s the max reported in the US.
• FEW045 — Cloud layer. Few clouds at 4,500 feet AGL. The number is in hundreds of feet.
• BKN090 — Second cloud layer. Broken at 9,000 feet AGL.
• 22/14 — Temperature/dewpoint in Celsius. 22°C temp, 14°C dewpoint.
• A2992 — Altimeter setting. 29.92 inches of mercury.
• RMK AO2 SLP132 T02220139 — Remarks section. Automated station with precipitation sensor, sea-level pressure, and precise temp/dewpoint data.

Station, time, wind, visibility, weather, clouds, temp/dewpoint, altimeter, remarks. That sequence never moves. Lock it in and a wall of letters stops being intimidating pretty fast.

The Elements That Matter Most

Probably should have opened with this section, honestly. Before you go memorizing every obscure code in the book, know which parts of a METAR are actually doing the heavy lifting on preflight day.

Wind — The First Thing I Check

Wind touches everything — runway selection, fuel burn, your approach, and when it gets gusty enough, your entire game plan. The wind group reads direction in degrees magnetic, then speed in knots. See a G in the middle — like 27018G28KT — that’s gusts. This one means 270° at 18 knots, gusting to 28. That 10-knot spread matters, especially in a light trainer. Anything past a 15-knot gust spread and I’m genuinely thinking hard about the airplane I’m flying and the runway waiting for me.

Variable winds show up as VRB. VRB04KT means light and swirly — not usually a problem. You’ll also see a direction variable group tacked on after the main wind, like 250V310, meaning the wind is wandering between 250° and 310°. That one matters on a crosswind runway. A lot.

Visibility — What the Number Actually Means

But what is the 10SM you keep seeing? In essence, it’s the reported ceiling on visibility in US METARs — meaning conditions are at least that good, not exactly that good. But it’s much more than that. Below 10SM, values get specific: 3SM, 1 1/2SM, or the one that gets your attention fast — 1/4SM. Quarter-mile visibility is essentially zero-zero for most general aviation pilots. Full stop.

Drop below 6SM and you’ll also see a present weather group appear before the cloud report — things like -RA (light rain), BR (mist), FG (fog), TSRA (thunderstorm with rain). These aren’t decoration. They explain the number you’re looking at.

Ceiling — The Number That Drives the Decision

The ceiling is the lowest broken (BKN) or overcast (OVC) layer. Not FEW. Not SCT. BKN or OVC — that’s the definition, legally and practically. A METAR showing FEW015 BKN080 has a ceiling of 8,000 feet, not 1,500, even though something is sitting at 1,500. FEW and SCT are just clouds in the sky. They’re not your ceiling.

VFR minimums in Class G airspace call for 1,000-foot ceiling and 3SM visibility during the day. Most pilots flying controlled airspace want considerably more breathing room. Personally, I won’t depart VFR into a forecast below 2,500 and 5SM — at least if I don’t have a solid alternate and a clear out already identified.

Temperature and Dewpoint — More Than Just Numbers

The spread between temperature and dewpoint is telling you something. Narrow spread — 2°C or less — means the air is close to saturation. Fog, low clouds, reduced visibility — especially overnight or early morning when temps drop toward the dewpoint. Don’t make my mistake: I once departed a mountain airport on a perfectly clear afternoon METAR, arrived two hours later, and found it fogged in completely — the spread had closed after sunset. Cost me a night in a $140 motel in a town with one restaurant and a gas station that closed at 8.

Temperature also flags your density altitude situation. Hot day, high elevation, and you’re running different numbers than on a cold winter morning at sea level. That math matters before you start the engine.

Altimeter Setting — Don’t Skip It

Set it before you taxi. Set it again at the hold short. The altimeter setting in the METAR gets you close. ATC gives you the current local setting in controlled airspace — but flying into an uncontrolled field, you’re working off whatever the nearest ASOS last reported. Within roughly 100nm, that’s close enough. Beyond that, find a closer source. Sloppy altimeter settings have a way of becoming serious problems in mountainous terrain or on instrument approaches.

Special Codes Pilots Miss

SPECI — When the Routine Isn’t Enough

Routine METARs drop once an hour at most automated stations — more often at busier airports. A SPECI is an unscheduled observation, automatically triggered when something significant changes fast. Visibility suddenly drops below 3SM. A thunderstorm rolls in or clears out. The ceiling falls below 3,000 feet. The system fires a SPECI without waiting for the top of the hour. If you’re pulling weather and a SPECI is sitting in the list, that’s the one you read first. Something changed — and it changed quickly.

FEW vs SCT vs BKN vs OVC — Get This Right

This trips up student pilots constantly. Cloud coverage is reported in eighths of sky called oktas — and which category a layer falls into determines whether it’s a ceiling or just scenery.

• FEW — 1 to 2 oktas. A few clouds. Not a ceiling.
• SCT (Scattered) — 3 to 4 oktas. Not a ceiling either.
• BKN (Broken) — 5 to 7 oktas. This IS a ceiling.
• OVC (Overcast) — 8 oktas. Complete coverage. Ceiling.
• SKC or CLR — Sky clear. SKC comes from human-staffed stations; CLR is automated, meaning no clouds below 12,000 feet.

VV — vertical visibility — replaces cloud layers when the sky is obscured entirely, like in heavy fog or dense smoke. VV004 means 400 feet of vertical visibility into the obscuration. That’s an IFR emergency for most of us flying piston singles.

The RMK Section — Where the Real Data Lives

Most pilots I trained with ignored the RMK section entirely. That’s a mistake — honestly, a pretty costly one in certain conditions. Remarks carry information that doesn’t fit the standard format, and some of it is genuinely useful.

• AO1 — Automated station without a precipitation discriminator. It knows something is falling — rain or snow, it can’t say.
• AO2 — Automated station with a precipitation discriminator. More reliable data.
• SLP — Sea-level pressure in hectopascals. SLP132 means 1013.2 hPa. (Prefix 9 or 10 — whichever puts you closer to 1000 hPa.)
• TSNO — Thunderstorm information not available. In convective season, this means the METAR won’t warn you about nearby thunder. Worth knowing before you assume the sky is clear of activity.
• PK WND — Peak wind. PK WND 35055/1423 means 350° at 55 knots at 14:23 Zulu. A data point worth sitting with for a moment.
• PRESFR / PRESRR — Pressure falling rapidly / rising rapidly. Either one signals something significant happening meteorologically — and neither one is the time to stop paying attention.

Quick Reference Decode Table

This is the section you print out. Laminate it. Tape it somewhere it won’t dissolve on a summer cross-country. These are the codes that show up most often in everyday GA flying — the ones worth knowing cold.

Report Type

• METAR — Routine hourly observation
• SPECI — Special unscheduled observation

Wind

• KT — Knots
• G — Gusts (e.g., 18G28KT)
• VRB — Variable direction
• 00000KT — Calm winds
• 250V310 — Wind varying between 250° and 310°

Visibility

• SM — Statute miles
• 10SM — 10 statute miles or more
• M1/4SM — Less than 1/4 statute mile

Present Weather

• RA — Rain
• SN — Snow
• DZ — Drizzle
• FG — Fog (visibility below 5/8 SM)
• BR — Mist (visibility 5/8 to 6 SM)
• HZ — Haze
• TS — Thunderstorm
• GR — Hail
• GS — Small hail or snow pellets
• FZRA — Freezing rain
• FZDZ — Freezing drizzle
• – prefix — Light intensity
• + prefix — Heavy intensity
• No prefix — Moderate intensity

Sky Condition

• SKC — Sky clear (human observation)
• CLR — Clear below 12,000 feet (automated)
• FEW — 1–2 oktas (not a ceiling)
• SCT — 3–4 oktas (not a ceiling)
• BKN — 5–7 oktas (ceiling)
• OVC — 8 oktas (ceiling)
• VV — Vertical visibility into obscuration
• CB — Cumulonimbus (appended to cloud group, e.g., BKN040CB)
• TCU — Towering cumulus

Temperature and Dewpoint

• Format: TT/DD in Celsius
• M prefix — Minus (below zero). M05/M12 = -5°C / -12°C

Altimeter

• A — Inches of mercury (US format, e.g., A2992)
• Q — Hectopascals (international format, e.g., Q1013)

Common Remarks Codes

• AO1 — Automated, no precipitation type sensor
• AO2 — Automated, with precipitation type sensor
• SLP — Sea-level pressure (hPa)
• PK WND — Peak wind direction, speed, and time
• WSHFT — Wind shift (followed by time)
• PRESFR — Pressure falling rapidly
• PRESRR — Pressure rising rapidly
• TSNO — Thunderstorm detection not available
• FZRANO — Freezing rain sensor not operating
• $ — System needs maintenance (appears at the very end of a METAR — don’t ignore this one)