The METAR, the Coded Surface Observation That Opens Every Weather Briefing, and the Sky Condition Groups Student Pilots Most Often Misread Before Their First Cross-Country

A METAR is a surface weather observation taken at a specific airport at a specific time. It reports actual, observed conditions at the moment of issuance - not a forecast. Reading the complete report, not just the altimeter setting, is what separates a prepared pilot from one who gets surprised.

What Is a METAR, and What Is a SPECI?

METARs are issued every hour, on the hour. When conditions change significantly between scheduled observations - a sudden drop in visibility, a sharp wind shift - the station issues a SPECI, a special observation. When SPECI appears at the top of a report, conditions changed fast enough that the station couldn’t wait for the next scheduled update. That alone signals something worth paying attention to.

The METAR reports what a sensor, or in some cases a trained observer, actually measured at the moment of issuance. It is not predictive.

How Do You Read the Station Identifier and Timestamp?

Every U.S. airport with a weather reporting station has a four-letter identifier beginning with K. Denver International is KDEN. Seattle’s Boeing Field is KBFI. Tampa International is KTPA. Find these on your sectional chart or in the Airport/Facility Directory when pulling METARs along a route.

Date and time are reported in Coordinated Universal Time (UTC), called Zulu. The format is a six-digit number followed by Z: the first two digits are the day of the month, the last four are the hour and minute. 091500Z means the ninth day of the month at 1500 Zulu. Get comfortable with Zulu-to-local conversion - you’ll do it for the rest of your flying career.

How Do You Decode Wind in a METAR?

Wind is reported as a three-digit direction followed by a two- or three-digit speed and the letters KT for knots. 18015KT means wind from due south at 15 knots.

One critical detail most students miss: wind direction in a METAR is referenced to true north, not magnetic north. Your runway numbers and heading indicator are magnetic. Depending on location, the difference between magnetic and true can exceed 15 degrees - enough to meaningfully change your crosswind component calculation. Always apply local magnetic variation to the METAR wind direction before running your crosswind math.

Gusts appear with the letter G: 18015G25KT means wind from the south at 15 knots, gusting to 25 knots. That’s a 10-knot spread. Always calculate your crosswind component using the peak gust, not the sustained wind.

VRB indicates variable winds: VRB02KT means light and variable. However, if you see a direction, then V, then a second direction - such as 150V240 - the wind is swinging between those two headings. If those headings straddle your runway alignment, that is a significant crosswind situation.

What Does Visibility Mean in a METAR?

Visibility is reported in statute miles in the United States. 10SM means ten statute miles or better - that’s the reporting ceiling. You won’t see 12 or 15 SM; anything at or above ten reads as 10SM. 3SM is three statute miles. 1/4SM is one-quarter mile.

Under FAR Part 91, VFR flight in most controlled airspace requires at least 3 statute miles of visibility. Values below that in a METAR indicate instrument meteorological conditions.

How Do You Read Present Weather Codes?

Between visibility and sky condition, short codes describe active precipitation or obscuration. The most common:

• RA - rain
• SN - snow
• TS - thunderstorm
• FG - fog
• BR - mist (visibility between 5/8 mile and 6 statute miles with high humidity)
• HZ - haze
• DZ - drizzle

Intensity modifiers use a minus sign for light (-RA = light rain) and a plus sign for heavy (+TSRA = heavy thunderstorm with rain).

If TS appears anywhere in the present weather section, there is an active thunderstorm at or in the immediate vicinity of the airport. This is not a factor to weigh against other conditions. It is a hard stop for VFR flight.

How Do You Determine the Ceiling From Sky Condition Groups?

This is the section most students rush through and most examiners probe. Sky conditions are reported in layers, lowest first, using a three-letter coverage code followed by a height in hundreds of feet above field elevation.

The FAA defines a ceiling as the lowest broken or overcast layer. For VFR flight in most controlled airspace, you need a ceiling of at least 1,000 feet AGL.

Two examples make this concrete:

FEW015 SCT030 BKN120 - The few layer at 1,500 feet is not a ceiling. The scattered layer at 3,000 feet is not a ceiling. The broken layer at 12,000 feet is your ceiling. Solid VFR.

BKN008 - Broken at 800 feet. Your ceiling is 800 feet. You are below the 1,000-foot VFR minimum. That is a no-go.

Those heights are above field elevation, not above sea level. At an airport sitting at 5,000 feet MSL, BKN008 puts the cloud base at 5,800 feet MSL. This matters when checking minimum en route altitudes through mountainous terrain.

If conditions are completely obscured - heavy fog, smoke, blowing snow - the report uses VV for vertical visibility: VV004 means the sensor can only see upward 400 feet. Vertical visibility counts as a ceiling for flight planning purposes.

What Does the Temperature-Dewpoint Spread Tell You?

Temperature and dewpoint are reported in Celsius, separated by a slash. 26/22 means 26°C temperature and 22°C dewpoint - a spread of 4 degrees.

A narrow spread means the air is near saturation, and fog or low clouds can form quickly. When the spread is 5°C or less, watch for deteriorating conditions. At 2–3 degrees, conditions can drop from decent VFR to IFR faster than an hourly METAR can capture.

This is especially important in the evening and overnight, when surface temperatures fall toward the dewpoint and radiation fog becomes possible. A 5-degree spread at noon can be a half-degree spread by midnight.

What Does the Altimeter Setting Tell You?

In the U.S., the altimeter setting appears as A followed by four digits. A2992 means 29.92 inches of mercury - standard sea level pressure. Significant deviations above or below that reflect the regional pressure gradient.

High pressure often brings clear skies but can trap haze near the surface, reducing visibility below what you’d expect on a clear day. Low pressure typically accompanies frontal weather with clouds and precipitation.

FAR Part 91 requires you to set your altimeter to the current local altimeter setting before operating in the vicinity of an airport. Within 100 nautical miles of your destination, update to that airport’s current setting.

What Is in the Remarks Section?

The remarks section carries more useful information than most students realize.

RMK AO2 means the station is an automated system with a precipitation discriminator - it can distinguish rain from snow. AO1 means automated without that capability. If you see AO1 and precipitation is reported, the system cannot identify what type is falling.

TSNO in remarks means the station has no thunderstorm sensor. This is critical: if TSNO appears, the automated station cannot detect thunderstorms. A cumulonimbus could be directly overhead and TS would not appear in the present weather section. When you see TSNO, your thunderstorm awareness depends entirely on radar, satellite, and pilot reports.

PWINO means the present weather identifier is offline. VISNO means the visibility sensor is down. When these appear, the report is less complete than it should be.

PK WND gives the peak wind since the last observation - direction, speed, and time. If that peak was significantly stronger than the sustained wind in the body of the report, plan around the peak. Gusts tend to recur.

LTG followed by a direction means lightning was observed. Even if the rest of the report looks manageable, lightning in remarks indicates convective activity in the area. That is a decision point, not a footnote.

SLP followed by numbers gives sea level pressure in hectopascals - useful context for the broader pressure pattern across your route.

How to Read a Complete METAR From Start to Finish

Here is a realistic observation from Savannah, Georgia, walked through group by group:

• Date/Time: 23rd at 1755Z
• Wind: From the east at 12 knots, no gusts
• Visibility: 10SM
• Sky condition: FEW025 OVC085 - ceiling is overcast at 8,500 feet
• Temperature/Dewpoint: 24°C / 19°C - spread of 5 degrees
• Altimeter: A2985
• Remarks: AO2, SLP1016.2

What this tells you: Ceiling is 8,500 feet - solid VFR. Visibility is 10 or better. Wind from the east at 12 knots means east-facing runway assignments. Temperature-dewpoint spread is 5 degrees, close enough to note but not alarming in the afternoon. Altimeter is near standard. No precipitation, no thunderstorm activity, no sensor failures. This is a legal VFR flight with workable conditions.

How Do You Use a METAR as an Actual Go/No-Go Tool?

The METAR was accurate when it was issued. By the time you’re reading it, it can be up to one hour old. Weather moves. One METAR is a data point, not a complete picture.

Effective preflight weather analysis means comparing multiple METARs along your route, looking at the trend in those observations over the past several hours, and layering in forecasts to understand where conditions are heading. That is what a standard briefing looks like when used as an actual decision-making tool.

On your private pilot checkride, the Airman Certification Standards require you to obtain and interpret a standard weather briefing. Examiners will hand you a briefing package and ask you to explain conditions at departure, en route, and destination. Practice walking through the entire report out loud: wind direction relative to your runway, temperature-dewpoint spread and what it implies, altimeter setting, and anything flagged in remarks. The examiner is looking for a pilot who reads the whole report.

The National Weather Service, NOAA’s Aviation Weather Center, and Chapter 7 of the FAA’s Aeronautical Information Manual are the primary references for aviation weather services. The AIM chapter goes deeper than most ground school textbooks and is worth reading independently.

Key Takeaways

• A METAR is an observed surface weather report, not a forecast. SPECI means conditions changed enough that the station couldn’t wait for the next scheduled observation.
• Wind direction in a METAR is true north - not magnetic. Apply local magnetic variation before calculating crosswind component, and always use the peak gust, not the sustained wind.
• The FAA ceiling definition is the lowest BKN or OVC layer. VFR in most controlled airspace requires a ceiling of at least 1,000 feet AGL and visibility of at least 3 statute miles.
• Sky condition heights are above field elevation, not sea level. A temperature-dewpoint spread of 5°C or less warrants close attention, especially in the evening and overnight.
• The remarks section contains critical operational information: TSNO means no thunderstorm detection capability; PWINO and VISNO mean sensors are offline; lightning in remarks means convective activity is in the area.