How to Read METAR Weather Reports – A Comprehensive Guide

What Is a METAR Report?

A METAR report, short for Meteorological Terminal Air Report (or Meteorological Aerodrome Report), is the standardized format for broadcasting current weather observations.

Consider it a highly efficient language for weather. Instead of lengthy descriptions, a METAR uses a specific code to convey critical data like wind speed, visibility, cloud cover, and temperature.

For any aviator, understanding these reports is essential—it’s the foundation of safe flight planning and execution.

How Often Are METAR Reports Issued?

METAR reports are issued on a consistent, predictable schedule—typically once every hour.

However, weather is notoriously unpredictable.

This combination of regular and special reports forms the foundation of aviation weather safety.

Decoding a METAR Report

A METAR report may appear as a cryptic string of letters and numbers, but it follows a precise structure designed for quick interpretation.

Each segment provides specific information in a predetermined order, covering everything from airport location to wind, visibility, and cloud cover.

1) The ICAO Designator

Every METAR report begins with its most fundamental identifier: the ICAO designator.

Airports in the contiguous United States begin with ‘K,’ such as FLAX for Los Angeles International Airport, while other countries use different prefixes to ensure each code remains globally unique.

2) Date and Time

Immediately after the location code comes the date and time stamp, presented as a six-digit group followed by a ‘Z’ (e.g., 151753Z).

Reading this format is simple: the first two digits are the day of the month, while the next four represent the time in hours and minutes (HHMM).

3) Wind Information

Wind information follows—critical data for pilots planning takeoffs and landings.

The first three digits (350) indicate the wind’s direction in degrees from true north, while the next two (15) represent its speed in knots (KT).

But wind isn’t always steady. Sudden increases in speed are reported as gusts, indicated by a ‘G’ after the sustained wind speed, followed by the peak gust.

You’ll also encounter two special cases: if the wind direction is variable (often when speed is 6 knots or fewer), it’s coded as VRB (e.g., VRB05KT). If there is no wind, the report will simply read 00000KT, indicating calm conditions.

4) Visibility

After wind data comes visibility, which measures the greatest horizontal distance at which you can see and identify prominent objects.

In the United States, visibility is measured in statute miles (SM). For example, 5SM indicates five statute miles.

Internationally, visibility is typically reported in meters, so a code like 5000 means 5,000 meters.

5) Weather Phenomena

Right after visibility, you’ll find codes for any significant weather phenomena occurring at the time of observation.

Weather codes are broken down by intensity, descriptor, and type:

• Intensity: A minus sign (-) indicates light intensity, a plus sign (+) signifies heavy intensity, and no sign implies moderate intensity.

• Precipitation: Common codes include RA (Rain), SN (Snow), DZ (Drizzle), and GR (Hail). For example, +SN means heavy snow.

• Obscuration: These codes describe phenomena that reduce visibility, such as FG (Fog), BR (Mist), HZ (Haze), and DU (Widespread Dust).

• Other Phenomena: Includes codes like TS (Thunderstorm), SH (Showers), and SQ (Squalls). These can be combined, as in TSA for a thunderstorm with moderate rain.

Pilots examine this section carefully as it directly affects flight conditions. A code like TS warns of potential turbulence and lightning, while FG confirms the reason for low visibility.

Now for a more challenging example, which might be issued as a SPEC report due to changing conditions:

SPEC KJFK 151753Z 18015G25KT 1/2SM +TSA FG BKN008 OVC015CB 18/17 A2988 RMK AO2 TSB25

This report paints a much more active weather picture:

• SPEC: This is a special, unscheduled report, indicating a significant weather change.

• JFK: The ICAO code for John F. Kennedy International Airport in New York.

• 151753Z: Issued on the 15th day of the month at 17:53 Zulu time.

• 18015G25KT: The wind is from 180 degrees (due south) at 15 knots, with gusts (G) up to 25 knots.

• 1/2SM: Visibility is significantly reduced to one-half of a statute mile.

• +TSA FG: This indicates heavy (+) thunderstorm (TS) with rain (RA) and fog (FG).

• BKN008 OVC015CB: The sky has a broken cloud layer at just 800 feet and an overcast layer at 1,500 feet. The presence of cumulonimbus (CB) clouds confirms a thunderstorm is active.

• 18/17: The temperature is 18°C, and the dew point is 17°C. The proximity of these two numbers indicates high humidity, consistent with the reported rain and fog.

• A2988: The altimeter setting is 29.88 inches of mercury.

• RMK AO2 TSB25: This is the remarks section. AO2 means the station is automated with a precipitation discriminator. TSB25 means the thunderstorm began at 25 minutes past the hour.

Comparing these examples shows how the standardized METAR format efficiently communicates conditions ranging from calm, clear weather to severe thunderstorms.

What’s the Difference Between METAR Reports and Tags?

METAR and TAF (Terminal Aerodrome Forecast) serve different purposes: METAR reports current weather, while TAF forecasts future conditions.

This difference appears in their content: METAR provides a precise, real-time weather picture, while TAF offers a 24- to 30-hour forecast.

Summary

Understanding METAR reports is a fundamental skill for anyone involved in aviation. To help you remember the most critical information, here’s a summary of the key points covered in this guide:

• Standardized Weather Reports: METAR provides a condensed, standardized snapshot of current airport weather, typically issued hourly.

• Essential Components: Every report includes the airport’s ICAO code, observation time in UTC, wind direction and speed, visibility, weather phenomena, cloud layers, temperature, dew point, and altimeter setting.

• Flight Safety: Pilots must quickly and accurately decode METAR reports to assess conditions and make safe operational decisions.

• Timely Updates: SPEC reports provide immediate updates when weather conditions change significantly between hourly reports.

• Regular Practice: Like any specialized language, proficiency develops through regular practice, making decoding intuitive and improving situational awareness.