Reading a METAR
A METAR (Meteorological Aerodrome Report) is the standard format for current, routine aviation weather observations, issued roughly every hour at thousands of airports. It looks like a dense string of letters and numbers, but every character has an exact, standardized meaning. This lesson decodes a real METAR field by field and gives you a working wind component calculator to turn the wind group into a headwind and crosswind number you can actually use for flight planning.
The example we'll decode
Here is a realistic METAR for a fictional airport, formatted exactly the way the National Weather Service and FAA publish them:
Every group between spaces carries a specific piece of information, always in the same order. Once you know the order, decoding any METAR — including one you've never seen before — is a mechanical process, not a memorization task.
Station identifier and date/time
KAPX is the four-letter ICAO identifier for the reporting station (the "K" prefix indicates the contiguous United States). 151853Z is the day of the month and time of the observation in Coordinated Universal Time (UTC), also called "Zulu" time: the 15th day of the month, at 1853Z (6:53 PM UTC). Aviation weather always uses Zulu time specifically to avoid confusion across time zones — a remote pilot must convert this to local time when planning a flight.
Wind: 22012G18KT
This is the most safety-critical group for a small sUAS. Reading left to right: 220 is the wind direction in degrees, measured clockwise from true north, meaning the wind is blowing FROM 220° (from the southwest). 12 is the sustained wind speed. G18 means the wind is gusting to 18 — a "G" always precedes the peak gust value when one is reported. KT confirms the unit is knots (1 knot ≈ 1.15 mph). A gust spread of 6 knots here (18 minus 12) is a meaningful sign of gusty, mechanically turbulent air, not just a strong steady breeze.
Occasionally you will see VRB in place of a three-digit direction (e.g. VRB03KT) — this means the wind direction is variable, typically reported when wind speed is very light and direction is inconsistent.
Visibility and sky condition: 10SM FEW050 SCT100 BKN250
10SM is prevailing visibility in statute miles — 10 or more miles is often reported simply as "10SM" even if technically greater. The sky condition groups that follow report cloud layers from lowest to highest: FEW050 means few clouds (1-2 oktas of coverage) with a base at 5,000 feet AGL (the last two digits are always in hundreds of feet — "050" = 5,000 ft). SCT100 means scattered clouds (3-4 oktas) at 10,000 feet. BKN250 means broken clouds (5-7 oktas) at 25,000 feet. A ceiling exists only where clouds are reported as broken (BKN) or overcast (OVC) — few and scattered layers are not considered a ceiling.
Temperature/dew point and altimeter: 24/12 A3002
24/12 reports temperature over dew point in whole degrees Celsius — 24°C temperature, 12°C dew point (see Lesson G for what this spread predicts about fog risk). A3002 is the altimeter setting: an "A" prefix means inches of mercury, so this reads 30.02 inHg — the value pilots set into an altimeter to read correct altitude for current barometric pressure at that station.
Remarks: RMK AO2 SLP158 T02440122
Everything after RMK is supplementary remarks. AO2 indicates an automated station with a precipitation-discriminating sensor. SLP158 is sea-level pressure in a shorthand format (1015.8 hPa). T02440122 is a more precise temperature/dew point readout to the tenth of a degree (024.4°C / 012.2°C) than the rounded whole-degree values reported earlier in the body of the report. Most remarks are not essential for a routine Part 107 go/no-go decision, but knowing the format prevents misreading a remark as part of the main body.
| Field example | Meaning | Unit/format | Notes |
|---|---|---|---|
| KAPX | Station identifier | 4-letter ICAO code | "K" prefix = contiguous United States |
| 151853Z | Day/time of observation | DDHHMMZ, UTC (Zulu) | Always UTC, never local time |
| 22012G18KT | Wind direction/speed/gust | Degrees true, knots | "VRB" replaces direction when winds are variable and light |
| 10SM | Prevailing visibility | Statute miles | "10SM" is often the reporting cap even if visibility is greater |
| FEW / SCT / BKN / OVC | Sky condition (cloud coverage) | Oktas of sky covered; altitude in hundreds of ft AGL | Only BKN/OVC counts as a ceiling |
| 24/12 | Temperature/dew point | Whole degrees Celsius | Narrow spread signals fog risk (Lesson G) |
| A3002 | Altimeter setting | Inches of mercury (A = inHg) | 30.02 inHg in this example |
Wind Component Calculator
Decoding Any METAR in Order
Follow the fields in this exact order — it never changes — and you can decode a METAR you've never seen before.
Identify the station and time
Read the 4-letter identifier, then the DDHHMMZ group. Convert the Zulu time to your local time zone before doing anything else.
Read the wind group
Direction, then speed, then gust (if present), then unit. Plug the direction and speed into the wind component calculator above to get a usable headwind/crosswind number for your flight direction.
Read visibility, then sky condition layers in order
Visibility comes first, then cloud layers from lowest to highest. Identify whether a ceiling exists (only BKN or OVC counts).
Read temperature/dew point and altimeter setting
Note the spread between temperature and dew point (Lesson G explains fog risk). Confirm the altimeter setting if you're comparing pressure trends across the day.
Scan the remarks section last
Remarks add detail but rarely change a go/no-go decision on their own. Confirm nothing unusual (like a "PRESRR" rapid pressure rise remark, signaling an approaching front) is flagged.
| Mistake | Why it happens | Correct understanding | Regulation / source |
|---|---|---|---|
| Reading wind speed as mph instead of knots | Most everyday speed references (car, weather app) use mph | METAR wind is always reported in knots (1 kt ≈ 1.15 mph) unless explicitly labeled otherwise | NWS METAR format standard |
| Treating the reported time as local time | Most everyday weather sources default to local time | METAR time is always UTC/Zulu — convert to local before planning | NWS METAR format standard |
| Counting FEW or SCT clouds as a ceiling | Any reported cloud layer sounds like it should count | Only BKN (broken) or OVC (overcast) layers are considered a ceiling | AC 107-2A |
| Ignoring the gust value and only reading sustained wind speed | The sustained number appears first and looks like "the" wind speed | The G-value shows peak gusts, which drive short-term control demands more than the sustained figure | AC 107-2A, Chapter 5 |
How often is a METAR updated?
Typically once per hour at most reporting stations, though a SPECI (special report) can be issued between routine hourly reports when conditions change significantly — for example, a sudden drop in visibility or a wind shift.
What does the "AUTO" modifier mean if I see it?
AUTO indicates the report was generated entirely by an automated weather station with no human observer augmentation. It does not mean the data is less reliable, but automated stations can occasionally miss certain phenomena (like some cloud types) that a human observer would catch.
Why does wind direction matter if my drone can fly in any direction equally?
Most small sUAS can technically move in any direction, but they are not equally efficient or stable doing so. Flying directly into a headwind uses more battery and gives better control authority; flying with a strong crosswind or tailwind can increase drift and reduce the margin for precise positioning, especially during takeoff and landing.
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Test Your Knowledge
Answer the questions below to check your understanding. Every answer can be found in the lesson above.