How to read a METAR and TAFAIM 7-1-28 Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR)
AIM 7-1-28 is a reference key to the codes in METAR weather reports and TAF forecasts, built around a sample report and forecast for KPIT. It explains each group in order (type, station, time, wind, visibility, weather, clouds, temperature and altimeter) and the TAF change groups FM, TEMPO, PROB and BECMG.
By the ATIS Alerts team · Updated October 15, 2026 · AIM effective July 9, 2026. A study aid based on the official AIM text, not legal advice or an FAA interpretation. The AIM is guidance; the regulations it points to are in 14 CFR.
At a glance
- All times are UTC ("Z"), written as a 2-digit date and 4-digit time, such as 091955Z.
- Wind is a 3-digit true-north direction to the nearest 10 degrees plus speed, with G for gusts and 00000KT for calm.
- Cloud amounts: SKC 0/8, FEW more than 0/8 to 2/8, SCT 3/8 to 4/8, BKN 5/8 to 7/8, OVC 8/8, with height in hundreds of feet.
- The key defines ceiling as the lowest broken or overcast layer, or the vertical visibility.
- Weather intensity: "-" is light, no sign is moderate, "+" is heavy; VC means in the vicinity but not at the aerodrome.
- TAF change groups: FM (from), TEMPO (temporary), PROB30 or PROB40 (probability) and BECMG (becoming).
In plain English
The AIM is guidance, and this paragraph is a reference key rather than a set of rules. It takes a sample TAF and METAR for KPIT and explains each group left to right, with the forecast column and the report column side by side. Many groups are explained once for both products, so learning one helps you read the other.
Here is the sample report: METAR KPIT 091955Z COR 22015G25KT 3/4SM R28L/2600FT TSRA OVC010CB 18/16 A2992 RMK SLP045 T01820159. Using the key, it is a corrected (COR) report from KPIT issued on the 9th at 1955 UTC. Wind is from 220 degrees true at 15 knots gusting 25, visibility is 3/4 statute mile, and the runway visual range for runway 28L is 2,600 feet. TSRA is a thunderstorm with moderate rain, OVC010CB is an overcast layer at 1,000 feet with cumulonimbus, 18/16 is a temperature of 18 and a dew point of 16 degrees Celsius, and A2992 is an altimeter setting of 29.92 inches. In the remarks, SLP045 is a sea-level pressure of 1004.5 hectopascals and T01820159 gives the temperature as 18.2 and the dew point as 15.9 degrees Celsius.
The sample TAF shows how forecasts are built. KPIT 091730Z 0918/1024 was issued on the 9th at 1730 UTC and is valid from 18Z on the 9th to 24Z on the 10th; the key says a valid period is either 24 or 30 hours. FM marks a significant change starting at a given date, hour and minute, TEMPO marks changes expected for less than 1 hour and, in total, less than half of the stated period, PROB30 or PROB40 gives the probability of a condition during the period, and BECMG marks a change expected during the stated period. In a US TAF, WS marks non-convective low-level wind shear at or below 2,000 feet (WS010/31022KT is wind shear at 1,000 feet with wind from 310 degrees at 22 knots above it), and P6SM means visibility above 6 statute miles.
The key adds a few cautions. It warns users to confirm the date and time in a TAF: FM 10 0000 is 0000Z on the 10th, not 1000Z. It also notes that NWS TAFs exclude BECMG groups and temperature forecasts and do not use PROB in the first 9 hours of a TAF, and that NWS METARs exclude trend forecasts.
Common mistakes
- Misreading TAF times. All times are UTC, and the key cautions that FM 10 0000 is 0000Z on the 10th, not 1000Z.
- Treating CLR and SKC as the same. CLR appears only in automated METAR reports and means clear below 12,000 feet; SKC is sky clear, 0/8.
- Dropping the zeros in cloud heights. Heights are in hundreds of feet, so OVC010 is 1,000 feet.
- Mixing up mist and fog. The weather table lists BR (mist) at 5/8 statute mile or more and FG (fog) at less than 5/8 statute mile.
The official text
AIM 7-1-28 as published on faa.gov, effective July 9, 2026.
| Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Front)
| TAF | KPIT 091730Z 0918/1024 15005KT 5SM HZ FEW020 WS010/31022KT FM091930 30015G25KT 3SM SHRA OVC015 TEMPO 0920/0922 1/2SM +TSRA OVC008CB FM100100 27008KT 5SM SHRA BKN020 OVC040 PROB30 1004/1007 1SM -RA BR FM101015 18005KT 6SM -SHRA OVC020 BECMG 1013/1015 P6SM NSW SKC | |
|---|---|---|
| NOTE: Users are cautioned to confirm DATE and TIME of the TAF. For example FM 10 0000 is 0000Z on the 10th. Do not confuse with 1000Z! | ||
| METAR KPIT 091955Z COR 22015G25KT 3/4SM R28L/2600FT TSRA OVC010CB 18/16 A2992 RMK SLP045 T01820159 | ||
Forecast | Explanation | Report |
TAF | Message type: TAF-routine or TAF AMD-amended forecast, METAR-hourly, SPECI-special or TESTM-non-commissioned ASOS report | METAR |
KPIT | ICAO location indicator | KPIT |
091730Z | Issuance time: ALL times in UTC “Z”, 2-digit date, 4-digit time | 091955Z |
0918/1024 | Valid period, either 24 hours or 30 hours. The first two digits of EACH four digit number indicate the date of the valid period, the final two digits indicate the time (valid from 18Z on the 9 th to 24Z on the 10 th) In U.S. METAR: CORrected ob or AUTOmated ob for automated report with no human intervention omitted when observer logs on. | COR |
15005KT | Wind: 3 digit true-north direction, nearest 10 degrees (or VaRiaBle) next 2-3 digits for speed and unit, KT (KMH or MPS) as needed, Gust and maximum speed 00000KT for calm for METAR, if direction varies 60 degrees or more, Variability appended, e.g., 180V260 | 22015G25KT |
5SM | Prevailing visibility in U.S., Statute Miles & fractions above 6 miles in TAF Plus6SM. (Or, 4-digit minimum visibility in meters and as required, lowest value with direction) Runway Visual Range: R 2-digit runway designator Left, Center, or Right as needed “/”, Minus or Plus in U.S., 4-digit value, FeeT in U.S., (usually meters elsewhere) 4-digit value Variability 4-digit value (and tendency Down, Up or No change) | ¾SM R28L/2600FT |
HZ | Significant present, forecast and recent weather: see table (on back) | TSRA |
FEW020 | Cloud amount, height and type: Sky Clear 0/8, FEW >0/8-2/8, ScaTtered 3/8-4/8, BroKeN 5/8-7/8, OverCast 8/8 3-digit height in hundreds of ft Towering Cumulus or CumulonimBus in METAR in TAF, only CB. Vertical Visibility for obscured sky and height “VV004”. More than 1 layer may be reported or forecast. In automated METAR reports only, CleaR for “clear below 12,000 feet” Temperature: degrees Celsius first 2 digits, temperature “/” last 2 digits, dew-point temperature Minus for below zero, e.g., M06 Altimeter setting: indicator and 4 digits in U.S., A-inches and hundredths (Q-hectoPascals, e.g., Q1013) | OVC 010CB 18/16 A2992 |
WS010/31022KT | In U.S. TAF, non-convective low-level (≤2,000 ft) Wind Shear 3-digit height (hundreds of ft) “/” 3-digit wind direction and 2-3 digit wind speed above the indicated height, and unit, KT | |
| | Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report (METAR) (Back) | ||
| In METAR, ReMarK indicator & remarks. For example: Sea- Level Pressure in hectoPascals & tenths, as shown: 1004.5 hPa Temp/dew-point in tenths °C, as shown: temp. 18.2°C, dew-point 15.9°C | RMK SLP045 T01820159 | |
FM091930 | FroM: changes are expected at: 2-digit date, 2-digit hour, and 2-digit minute beginning time: indicates significant change. Each FM starts on a new line, indented 5 spaces | |
TEMPO 0920/0922 | TEMPOrary: changes expected for <1 hour and in total, < half of the period between the 2-digit date and 2-digit hour beginning, and 2-digit date and 2-digit hour ending time | |
PROB30 1004/1007 | PROBability and 2-digit percent (30 or 40): probable condition in the period between the 2-digit date & 2-digit hour beginning time, and the 2-digit date and 2-digit hour ending time | |
BECMG 1013/1015 | BECoMinG: change expected in the period between the 2-digit date and 2-digit hour beginning time, and the 2-digit date and 2-digit hour ending time | |
Table of Significant Present, Forecast and Recent Weather - Grouped in categories and used in the order listed below; or as needed in TAF, No Significant Weather.
Qualifiers
Intensity or Proximity
| “-” = Light | No sign = Moderate | “+” = Heavy |
|---|
“VC” = Vicinity, but not at aerodrome. In the US METAR, 5 to 10 SM from the point of observation. In the US TAF, 5 to 10 SM from the center of the runway complex. Elsewhere, within 8000m.
Descriptor
| BC – Patches | BL – Blowing | DR – Drifting | FZ – Freezing |
|---|---|---|---|
MI – Shallow | PR – Partial | SH – Showers | TS – Thunderstorm |
| Weather Phenomena | |||
| Precipitation | |||
DZ – Drizzle | GR – Hail | GS – Small Hail/Snow Pellets | |
IC – Ice Crystals | PL – Ice Pellets | RA – Rain | SG – Snow Grains |
SN – Snow | UP – Unknown Precipitation in automated observations | ||
| Obscuration | |||
BR – Mist (≥5/8SM) | DU – Widespread Dust | FG – Fog (<5/8SM) | FU – Smoke |
HZ – Haze | PY – Spray | SA – Sand | VA – Volcanic Ash |
| Other | |||
DS – Dust Storm | FC – Funnel Cloud | +FC – Tornado or Waterspout | |
PO – Well developed dust or sand whirls | SQ – Squall | SS – Sandstorm | |
- Explanations in parentheses “()” indicate different worldwide practices.
- Ceiling is not specified; defined as the lowest broken or overcast layer, or the vertical visibility.
- NWS TAFs exclude BECMG groups and temperature forecasts, NWS TAFS do not use PROB in the first 9 hours of a TAF; NWS METARs exclude trend forecasts. US Military TAFs include Turbulence and Icing groups.
Test yourself
Practice questions from our free FAA written test prep that cite AIM 7-1-28.
Sport Pilot
In the METAR group 12008KT, the wind is reported as:
- A. from 120° true at 8 knots.
- B. from 120° magnetic at 8 knots.
- C. toward 120° at 8 knots.
- D. from 012° at 80 knots.
Show answer
A. from 120° true at 8 knots. METAR winds are given in degrees TRUE and the direction the wind is coming FROM. Tower and ATIS winds, by contrast, are magnetic: that difference is what makes a reported wind seem to disagree with the runway you were assigned.
More Sport Pilot practice →Recreational Pilot
In a TAF, the group TEMPO 1215/1218 indicates:
- A. temporary conditions expected between 1500Z and 1800Z on the 12th, each lasting less than one hour.
- B. a permanent change beginning on the 12th at 1500Z.
- C. conditions expected from the 15th through the 18th of the month.
- D. a gradual change occurring over three hours.
Show answer
A. temporary conditions expected between 1500Z and 1800Z on the 12th, each lasting less than one hour. TAF time groups are day and hour: 1215/1218 runs from the 12th at 1500Z to the 12th at 1800Z. TEMPO covers temporary fluctuations expected to last less than an hour each and, in total, less than half the period. FM marks a rapid permanent change, and BECMG a gradual one.
More Recreational Pilot practice →ATP Multiengine
In a TAF, the abbreviation PROB40 indicates:
- A. a 40 percent probability of the described conditions occurring.
- B. conditions expected to persist for 40 minutes.
- C. a 40 percent reduction in visibility.
- D. wind gusts to 40 knots.
Show answer
A. a 40 percent probability of the described conditions occurring. PROB30 and PROB40 express a 30 to 49 percent chance: below 30 percent the condition is not forecast at all, and at 50 percent or above it goes in the main forecast or a TEMPO, BECMG, or FM group. The NWS rule barring PROB30 from the first 9 hours of a TAF ended in September 2024, aligning U.S. TAFs with ICAO.
More ATP Multiengine practice →Basic Ground Instructor
A METAR reads: 'METAR KORL 121853Z 09008KT 4SM HZ BKN025 30/24 A2992'. The ceiling being reported is:
- A. 2,500 feet AGL.
- B. 2,500 feet MSL.
- C. 25,000 feet AGL.
- D. there is no ceiling: broken layers do not count.
Show answer
A. 2,500 feet AGL. In a METAR, cloud heights are given in hundreds of feet AGL, and a ceiling is the lowest broken or overcast layer. BKN025 is therefore a 2,500-foot AGL ceiling. In PIREPs, by contrast, cloud heights are MSL, a distinction students routinely miss.
More Basic Ground Instructor practice →
Questions pilots ask
How do you read a METAR?
Read it left to right: report type, station, date and time in UTC, wind, visibility and runway visual range, weather, clouds, temperature and dew point, altimeter setting, then remarks after RMK. AIM 7-1-28 decodes each group using a sample KPIT report.
What is the difference between TEMPO and BECMG in a TAF?
The AIM key describes TEMPO as changes expected for less than 1 hour and, in total, less than half of the stated period, and BECMG as a change expected during the stated period (AIM 7-1-28). It also notes that NWS TAFs exclude BECMG groups.
What does VC mean in a METAR?
VC means in the vicinity but not at the aerodrome. In a US METAR it is 5 to 10 statute miles from the point of observation, and in a US TAF 5 to 10 statute miles from the center of the runway complex (AIM 7-1-28, weather table).
Is the wind in a METAR true or magnetic?
The AIM key describes METAR and TAF wind as a 3-digit true-north direction to the nearest 10 degrees (AIM 7-1-28).