How to Read a METAR: A Group-by-Group Guide for Drone Pilots

A METAR is the coded weather observation from an airport's weather station. It looks like a jumble of letters and numbers, but each report follows a set format (Aviation Weather Handbook, p. 24-7), so reading one is mostly a matter of knowing what sits in each position. This guide takes the groups in the order you meet them, shows how to pick out the ceiling, and finishes with a made-up report to decode and judge against the Part 107 weather limits.

Plenty of briefing services and weather apps print a plain-language version beside the code. Even so, the FAA wants every pilot able to decode the original, in case a source doesn't offer the decoded text (Aviation Weather Handbook, p. 24-5).

Why a drone pilot should care

Before each flight, the remote pilot in command must assess the local weather (14 CFR 107.49(a)(1)). During the flight, the drone has to stay inside the Part 107 weather limits: flight visibility of at least 3 statute miles from the control station, and at least 500 feet below and 2,000 feet horizontally from any cloud (14 CFR 107.51(c) and (d)). FAA guidance lists local aviation weather reports as one way to check visibility and cloud clearance. If several reporting stations are nearby, it says to choose the closest one that is most representative of the terrain around your site (AC 107-2A, para. 5.12.3). METARs are free on the National Weather Service's Aviation Weather Center website, which FAA guidance encourages remote pilots to use (AC 107-2A, para. B.3.1). And aviation weather sources are one of the knowledge areas the Part 107 test covers (14 CFR 107.73(c)).

The order of the groups

A routine report is labeled METAR and is produced near the top of each hour. When conditions change enough between those times, for example when the visibility falls below 3 miles, the station sends an unscheduled report labeled SPECI, which carries all the same elements (Aviation Weather Handbook, p. 24-6). In the handbook's format, the groups run in this order: report type, station, date and time, a modifier if there is one, wind, visibility, runway visual range, present weather, sky condition, temperature and dew point, and altimeter. Remarks come last, after the letters RMK (Aviation Weather Handbook, pp. 24-8 to 24-18). Runway visual range only shows up at equipped airports in low visibility (Aviation Weather Handbook, p. 24-11), and any element that doesn't occur, or can't be observed, is simply missing from that report (Aviation Weather Handbook, p. 24-7).

• Station: a four-letter ICAO code. Airports in the contiguous U.S. use K plus their three-letter identifier; Alaska codes start with PA and Hawaii codes with PH (Aviation Weather Handbook, p. 24-8).
• Date and time: two digits for the day of the month, four for the hour and minutes, and a Z for UTC (Aviation Weather Handbook, p. 24-9). 121753Z means 1753 UTC on the 12th, whatever your local clock says.
• Modifier: AUTO when the report is fully automated with no human oversight, or COR in its place when the report corrects an earlier one (Aviation Weather Handbook, p. 24-9).

Wind

The wind group packs three facts into a few characters (Aviation Weather Handbook, p. 24-10):

• Direction: the first three digits, in degrees from true north. It is where the wind comes from, not where it is going.
• Speed: the next two or three digits, in knots, closed by KT. Direction and speed are both two-minute averages.
• Gusts: a G followed by the highest speed. Gusts are rapid swings in speed of 10 knots or more between peaks and lulls.

So 19016G26KT reads as from 190° true at 16 knots, gusting to 26. The same page covers three more forms. At 6 knots or less, the direction may be replaced by VRB, as in VRB04KT. Above 6 knots, a direction that wanders through 60° or more gets a second group with the two extremes, as in 25012KT 220V290. And 00000KT is calm.

Watch the reference, too. When ASOS reports are sent out nationally, on the internet for example, wind direction is in degrees true; the station's local radio and telephone broadcasts give it in degrees magnetic (Aviation Weather Handbook, p. 24-3).

Visibility and present weather

Visibility is given in statute miles and ends in SM. A space separates a whole number from a fraction, so one and a half miles is 1 1/2SM, and automated stations put an M in front to mean less than, as in M1/4SM (Aviation Weather Handbook, p. 24-11). Keep in mind that this is the visibility at the station. Part 107 is about flight visibility seen from your control station (14 CFR 107.51(c)), so use the report to know what to expect, then look for yourself.

Each present weather group is put together in a fixed sequence: an intensity or proximity sign, then a descriptor, then the weather. A minus sign means light, a plus sign means heavy, and no sign means moderate. A report holds no more than three of these groups (Aviation Weather Handbook, p. 24-12). Codes you will see often, all from the same table:

• Precipitation: RA rain, DZ drizzle, SN snow.
• Obscurations: BR mist, FG fog, HZ haze.
• Descriptors: SH showers, TS thunderstorm, FZ freezing.

Put together, +SHRA is heavy rain showers and -RA BR is light rain with mist. VC means the weather is in the vicinity, 5 to 10 statute miles from the station, rather than at it (Aviation Weather Handbook, p. 24-13). At ASOS stations, fog is reported as FG below 5/8 mile; from 5/8 mile to under 7 miles the station reports mist if the temperature and dew point are within about 2 °C (4 °F) of each other, and haze if they are further apart (Aviation Weather Handbook, p. 24-3).

Automated thunderstorm reports depend on how far away lightning is detected: TS in the body for lightning within 5 nautical miles of the airport, VCTS for 5 to 10 nautical miles, and LTG DSNT in the remarks from 10 to 30 nautical miles (Aviation Weather Handbook, p. 24-21).

Clouds and the ceiling

Each sky condition group is a cover amount followed by the height of the layer's base, in feet above ground level. Layers are listed from lowest to highest, and the list ends at the first overcast layer (Aviation Weather Handbook, p. 24-15). The height is in hundreds of feet, and the amounts are in eighths of the sky (Aviation Weather Handbook, p. 24-16):

• FEW covers up to 2/8 of the sky (any amount under 1/8 also counts as FEW).
• SCT, scattered, covers 3/8 or 4/8.
• BKN, broken, covers 5/8, 6/8 or 7/8.
• OVC, overcast, covers the whole sky.

BKN028 is therefore a broken layer based at 2,800 feet AGL. The ceiling is the lowest layer aloft reported as broken or overcast; when ground-based clouds hide the whole sky, the vertical visibility, coded VV, is the ceiling instead (Aviation Weather Handbook, p. 24-16).

Two pairs of codes are easy to mix up. SKC comes from a human observer and means no layers were seen. CLR comes from an automated station and only means its sensor found no layers up to 12,000 feet, so cloud above that is still possible (Aviation Weather Handbook, p. 24-16). And the cloud types CB (cumulonimbus) and TCU (towering cumulus) are appended to a layer at manual stations (Aviation Weather Handbook, p. 24-17), so an automated report may not mention them.

For a drone, the ceiling isn't the only number that matters. FEW and SCT layers never make a ceiling, but the 500-foot and 2,000-foot cloud distances in Part 107 apply to every cloud (14 CFR 107.51(d)).

Temperature, dew point and altimeter

Temperature and dew point are whole degrees Celsius, with M for minus: M03/M08 is a temperature of −3 °C and a dew point of −8 °C. The altimeter setting follows the letter A, in inches of mercury with the decimal point left out, so A2987 is 29.87 (Aviation Weather Handbook, p. 24-18).

Remarks worth knowing

• AO1 or AO2: an automated station without (AO1) or with (AO2) a precipitation discriminator (Aviation Weather Handbook, p. 24-20).
• PK WND 20031/28: the peak wind since the last METAR, from 200° at 31 knots, at 28 minutes past the hour (Aviation Weather Handbook, p. 24-20). A remark time in the same hour as the report is written as minutes only (Aviation Weather Handbook, p. 24-19).
• TSB or TSE with a time: when a thunderstorm began or ended (Aviation Weather Handbook, p. 24-22).
• PRESRR or PRESFR: at designated stations, pressure rising or falling at 0.06 inch per hour or more (Aviation Weather Handbook, p. 24-24).
• SLP: sea level pressure, in millibars to a tenth, minus its hundreds and thousands digits, which you fill back in: SLP112 stands for 1,011.2 millibars (Aviation Weather Handbook, p. 24-24).
• T group: temperature and dew point to a tenth of a degree. In T01610139, the 0 after the T means above zero and 161 is 16.1 °C; the next 0 means above zero and 139 is 13.9 °C (Aviation Weather Handbook, p. 24-25).

Practice: decode a made-up report

We wrote this report for practice. No station ever sent it, so treat it as an exercise, not a real Wichita observation; it doesn't come from FAA material either. Decode it yourself first, then check your reading in our free METAR and TAF decoder.

METAR KICT 121753Z 19016G26KT 5SM -RA BR FEW007 SCT015 BKN028 OVC050 16/14 A2987 RMK AO2 PK WND 20031/28 SLP112 T01610139

• METAR KICT 121753Z: a routine report from station KICT, the 12th at 1753 UTC.
• 19016G26KT: wind from 190° true at 16 knots, gusting to 26.
• 5SM -RA BR: visibility 5 statute miles in light rain and mist.
• FEW007 SCT015 BKN028 OVC050: few clouds at 700 feet, scattered at 1,500, broken at 2,800 (the ceiling) and overcast at 5,000, all AGL.
• 16/14 A2987: 16 °C, dew point 14 °C, altimeter 29.87.
• RMK AO2 PK WND 20031/28 SLP112 T01610139: automated station with a precipitation discriminator; peak wind from 200° at 31 knots at 1728 UTC; sea level pressure 1,011.2 millibars; 16.1 °C with a dew point of 13.9 °C.

Is it a drone day? The station's 5 miles is above the 3-mile minimum, and the 2,800-foot ceiling is far above the 400-foot altitude limit (14 CFR 107.51(b)). The cloud that limits you is the lowest one. Any time one of those few clouds at 700 feet drifts within 2,000 feet sideways of your drone, the 500-foot rule holds you at 200 feet AGL or lower (14 CFR 107.51(d)). Then there is the wind: compare the 26-knot gusts and the 31-knot peak with what your aircraft can handle. FAA guidance encourages manufacturers to give remote pilots limits for wind, precipitation and maximum gusts (AC 107-2A, para. 8.12.2.5.1). If those numbers are beyond your aircraft or your experience, waiting for a later report is the sensible call.

Quick checks before you trust a report

• The wind direction is where the wind comes from, in degrees true in the written report.
• Every time is UTC, including the times in the remarks.
• Only BKN, OVC or VV makes a ceiling, but every layer counts for cloud clearance.
• CLR only covers 12,000 feet and below.
• The report describes the station, not your site, so check the conditions where you fly.

Keep practicing

Weather is one of the five topics our practice questions cover, and the free weather sample questions include METAR groups with full explanations. Test yourself across every topic with the free 20-question Part 107 practice test, and look up any term in the Part 107 glossary. When you want more, Part 107 Complete ($39, one-time) adds the full weather lessons and a METAR and TAF trainer with a group-by-group decoder and practice drills. Next, read how to read a TAF, the forecast that uses the same codes, and how density altitude affects your drone.

Questions people ask

What does CLR mean in a METAR?

CLR means an automated station detected no cloud layers at or below 12,000 feet. It says nothing about clouds higher than that. SKC is different: it means an observer saw no layers (Aviation Weather Handbook, p. 24-16).

Is the wind in a METAR true or magnetic?

When ASOS reports are distributed nationally, such as on the internet, wind direction is in degrees true. The station's local radio and telephone broadcasts give it in degrees magnetic (Aviation Weather Handbook, p. 24-3).

How do I find the ceiling in a METAR?

Find the lowest layer reported as BKN (broken) or OVC (overcast). If ground-based clouds hide the whole sky, the vertical visibility (VV) is the ceiling. FEW and SCT layers are never the ceiling (Aviation Weather Handbook, p. 24-16).

Does a good METAR mean I can legally fly?

Not on its own. Part 107 measures flight visibility from your control station and requires 500 feet below and 2,000 feet horizontally from every cloud (14 CFR 107.51). A METAR describes the station, so choose the closest station that best represents your site's terrain (AC 107-2A, para. 5.12.3) and check the conditions where you are.