A METAR looks like a line of random code, and then one day it clicks and you read it like a sentence. The FAA knowledge test asks you to decode METARs and TAFs, and it also asks the questions around them: what counts as a ceiling, which direction a wind is measured from, when the next report is due. This guide gives you a fixed order to read them in, so you never skip a group.
Read a METAR in order: station, time (Zulu), wind, visibility (statute miles), weather, sky condition, temperature/dewpoint, altimeter (inches of mercury), remarks. The ceiling is the lowest broken or overcast layer. METAR winds are true; tower and ATIS winds are magnetic. A TAF is the forecast for the same airport, built from a base forecast plus FM, TEMPO and BECMG groups.
Reading a METAR, Group by Group
Here is a routine METAR:
KSRQ 221953Z 14009KT 10SM FEW025 BKN040 31/22 A3002 RMK AO2 SLP165
| Group | Meaning |
|---|---|
| KSRQ | Station: Sarasota-Bradenton. In the contiguous US the identifier starts with K |
| 221953Z | Day 22 of the month, 1953 UTC (Zulu). All times are in UTC |
| 14009KT | Wind from 140° true at 9 knots |
| 10SM | Visibility 10 statute miles (or more) |
| FEW025 BKN040 | Few clouds at 2,500 feet AGL, broken layer at 4,000 feet AGL. The ceiling is 4,000 feet |
| 31/22 | Temperature 31 °C, dewpoint 22 °C |
| A3002 | Altimeter setting 30.02 inches of mercury |
| RMK AO2 SLP165 | Remarks: automated station with a precipitation sensor, sea-level pressure 1016.5 hPa |
Wind
Wind is direction (three digits, degrees true) plus speed (knots). A G adds gusts: 34012G19KT is from 340° at 12 knots gusting to 19. VRB means variable direction, and 00000KT is calm. If the direction varies by 60° or more, an extra group such as 250V310 follows.
The classic trap: the METAR wind is true, while the wind a tower or ATIS gives you is magnetic, because that is what you compare against runway numbers.
Visibility
Visibility is in statute miles, with fractions written like 1 1/2SM. There is no CAVOK in the US, and visibility is shown as 10SM when it is 10 miles or more.
Present Weather
When something is happening, it comes after the visibility. The code is built from parts:
- Intensity: - light, no sign for moderate, + heavy
- Descriptor: TS thunderstorm, SH showers, FZ freezing
- Phenomenon: RA rain, SN snow, DZ drizzle, FG fog, BR mist, HZ haze
So -RA BR is light rain with mist, and +TSRA is a thunderstorm with heavy rain. FG is reported when visibility is below 5/8 of a mile, and BR when it is 5/8 to 6 miles.
Sky Condition and the Ceiling
Each layer gives a cover code and a height in hundreds of feet above ground level:
| Code | Meaning | Coverage |
|---|---|---|
| FEW | Few | Up to 2/8 of the sky |
| SCT | Scattered | 3/8 to 4/8 |
| BKN | Broken | 5/8 to 7/8 |
| OVC | Overcast | 8/8 |
| CLR / SKC | Clear | No clouds |
| VV | Vertical visibility | Sky obscured (fog, snow) |
The ceiling is the lowest layer that is broken or overcast, or the vertical visibility. FEW and SCT layers are never a ceiling. In FEW025 BKN040 OVC080, the ceiling is 4,000 feet, because 4,000 is the lowest broken or overcast layer.
Temperature, Dewpoint and Altimeter
Temperature and dewpoint are in degrees Celsius, separated by a slash, and a minus is written M: M02/M05 is -2 °C and -5 °C. When the spread between temperature and dewpoint is small (about 3 °C or 5 °F) and shrinking, expect fog or low clouds. The altimeter group is A followed by four digits: A2992 is 29.92 inches.
Remarks
Everything after RMK is extra information. AO2 is an automated station that can sense precipitation. A code such as RAB35 means rain began at 35 minutes past the hour, which is a favorite test question. SLP165 is sea-level pressure.
Flight Categories
Pilots sort the weather into four categories. The worse of the ceiling and visibility decides.
| Category | Ceiling | Visibility |
|---|---|---|
| VFR | Above 3,000 feet | Above 5 miles |
| MVFR | 1,000 to 3,000 feet | 3 to 5 miles |
| IFR | 500 to below 1,000 feet | 1 to below 3 miles |
| LIFR | Below 500 feet | Below 1 mile |
Try one: KORD 031451Z 04012G20KT 1 1/2SM -RA BR OVC008 09/08 A2987. Wind from 040° at 12, gusting 20; visibility 1 1/2 miles in light rain and mist; overcast at 800 feet. The ceiling is 800 feet (IFR) and the visibility is 1 1/2 miles (IFR), so this is IFR.
When Is the Next METAR?
Routine METARs are issued hourly, at about 53 minutes past the hour. If conditions change significantly between reports, a SPECI is issued. So a METAR stamped 221953Z is followed by the next routine report around 2053Z.
Reading a TAF
A TAF is a forecast for the area within about 5 statute miles of the airport. Most are valid for 24 hours, some for 30, and they are routinely issued four times a day.
TAF KMEM 031720Z 0318/0424 18010KT P6SM SCT050 FM032200 20012G22KT P6SM BKN060 TEMPO 0400/0403 3SM TSRA BKN030CB FM040600 VRB03KT 5SM BR OVC008
| Group | Meaning |
|---|---|
| TAF KMEM | Forecast for Memphis |
| 031720Z | Issued on the 3rd at 1720 UTC |
| 0318/0424 | Valid from the 3rd at 18Z to the 4th at 24Z (30 hours) |
| 18010KT P6SM SCT050 | Starting conditions: wind from 180° at 10, visibility plus 6 miles, scattered at 5,000 |
| FM032200 … | From 2200Z on the 3rd, all conditions change to the new group |
| TEMPO 0400/0403 … | Temporarily, between 00Z and 03Z on the 4th, thunderstorms and 3 miles visibility |
| FM040600 … | From 0600Z on the 4th, light variable winds, mist, overcast at 800 feet |
The key words:
- FM (from): a rapid, complete change at the stated time. It replaces everything before it.
- BECMG (becoming): a gradual change over the stated period, after which the new conditions stay.
- TEMPO: temporary fluctuations, each lasting less than an hour and covering less than half of the period.
- PROB30 / PROB40: a 30 or 40 percent chance.
- P6SM: visibility greater than 6 statute miles.
Common Exam Traps
- Ceiling: FEW and SCT layers do not make a ceiling. Only BKN, OVC or VV does.
- True or magnetic: METAR and TAF winds are true. Tower, ATIS and AWOS winds are magnetic.
- Units: visibility is in statute miles, altimeter in inches of mercury, temperature in Celsius, and cloud heights are AGL.
- FM versus TEMPO: FM replaces the previous conditions. TEMPO adds a short-lived change on top of them.
- Zulu time: every time is UTC. Convert to local time before you decide when a forecast applies to you.
Practice It
Decoding becomes automatic after a few dozen reports. AltiPrep FAA has weather questions with real METAR and TAF figures and a written explanation after each answer, so you can check your decoding as you go.
This article is a study aid. For official weather information, use current FAA and National Weather Service sources, and a flight service briefing at 1-800-WX-BRIEF or 1800wxbrief.com.
Keep reading: FAA Private Pilot Knowledge Test: Format, Subjects and How to Pass · Weight and Balance Explained · Wind Correction and Heading Conversion · VFR Weather Minimums and Airspace Classes · Stalls and Load Factor Explained
Frequently asked questions
What is the difference between a METAR and a TAF?
A METAR is an observation: it reports the weather actually measured at an airport, normally once an hour. A TAF is a forecast for the area within about 5 statute miles of an airport, usually covering 24 or 30 hours. Use the METAR for what is happening now and the TAF for what to expect.
Is the wind in a METAR true or magnetic?
METAR and TAF winds are given relative to true north. Winds reported by a tower, an ATIS or an AWOS are given relative to magnetic north, so they line up with runway numbers. The test likes to ask about this difference.
What are the four flight categories?
VFR is a ceiling above 3,000 feet and visibility above 5 miles. MVFR is a ceiling of 1,000 to 3,000 feet and/or visibility of 3 to 5 miles. IFR is a ceiling of 500 to below 1,000 feet and/or visibility of 1 to below 3 miles. LIFR is a ceiling below 500 feet and/or visibility below 1 mile. The worse of the ceiling and the visibility sets the category.
What counts as a ceiling in a METAR?
The ceiling is the height above ground level of the lowest layer reported as broken (BKN) or overcast (OVC), or the vertical visibility (VV) into an obscuration. Few (FEW) and scattered (SCT) layers are never a ceiling.
How long is a TAF valid?
Most TAFs are valid for 24 hours, and some airports have 30-hour TAFs. They are routinely issued four times a day and amended when conditions change.