The METAR Decode, the Two-Letter Sky Condition Code That Hides a Ceiling, and the TAF That Tells You Whether the Weather Will Hold for Your Return

A METAR is a standardized, hourly observation of actual weather conditions at a specific airport. A TAF is the corresponding terminal forecast. Together, they form the core of every preflight weather briefing - and if you can’t read both fluently, you’re making go/no-go decisions on incomplete information.

What Is a METAR and Why Does It Matter?

METAR stands for Meteorological Terminal Air Report. It is not a model output, a satellite estimate, or a consumer weather app summary. It is a direct measurement of conditions at a specific location at a specific time.

Routine METARs are issued at the top of every hour. When conditions change significantly between scheduled reports - a new ceiling, a visibility drop, a wind shift - a special observation is issued with the prefix SPECI. Multiple SPECI reports in a short window mean something is actively happening at that airport.

The METAR is the raw data behind every VFR go/no-go decision. Read it that way.

How Do I Identify the Station and Observation Time?

The first element is the station identifier. In the United States, most airports use a K prefix followed by the three-letter airport code (for example, KIND for Indianapolis International). Canadian airports typically start with C. International identifiers follow their own conventions.

The observation time follows as four digits plus the letter Z, meaning Zulu (Coordinated Universal Time). 2355Z means twenty-three fifty-five UTC. Know your local offset: Eastern Standard Time is UTC minus 5 hours; Eastern Daylight Time is UTC minus 4 hours. This trips up pilots more often than it should.

The word AUTO after the time means the station is automated with no human observer. Automated stations are reliable for what they measure, but they don’t catch everything a trained observer would. Keep that in mind when conditions are marginal.

How Do I Read Wind in a METAR?

Wind is reported as direction in degrees magnetic (the direction the wind is coming from) followed by speed in knots. An example: 36012G18KT means winds from 360 degrees (due north) at 12 knots, gusting to 18 knots.

VRB instead of a direction means variable winds, typically light and shifting under 6 knots. Calm winds appear as 00000KT. The gust value is the peak - a 12-knot wind gusting to 18 means your actual touchdown condition may be 6 knots more aggressive than the base speed suggests. Factor that into your crosswind planning before you ever call ground.

How Do I Decode Visibility?

Visibility in a U.S. METAR is always in statute miles, not nautical miles. Ten statute miles is the standard maximum reported value.

When visibility falls below 3 miles, you’ll see fractions: 1½, ¾, ¼. The prefix M means less than that value - M¼ means visibility is below a quarter mile. That is effectively zero-zero.

Visibility can change fast. A ten-mile morning METAR can become a half-mile METAR in twenty minutes when radiation fog settles in. The trend matters as much as the current number.

What Do Sky Condition Codes Mean - and Which Ones Establish a Ceiling?

This is the element that causes the most confusion, both on checkride day and in real-world preflight planning.

Sky condition codes use two- to three-letter abbreviations followed by a cloud height in hundreds of feet above ground level (AGL):

• FEW - 1 to 2 eighths sky coverage
• SCT (Scattered) - 3 to 4 eighths sky coverage
• BKN (Broken) - 5 to 7 eighths sky coverage
• OVC (Overcast) - total sky coverage

The ceiling is defined as the lowest broken or overcast layer. FEW and SCT do not establish a ceiling. Only BKN and OVC do.

A reading of BKN020 means a ceiling at 2,000 feet AGL. Under VFR, you must remain 500 feet below clouds in controlled airspace. A 2,000-foot ceiling leaves 1,500 feet of legal VFR airspace above the surface. That is not a comfortable margin.

OVC005 with ½SM visibility is Instrument Meteorological Conditions (IMC). That airport is closed to VFR operations unless you hold an instrument rating and your aircraft is properly equipped and current for the approach.

How Do Temperature and Dew Point Affect My Decision?

Temperature and dew point appear together in degrees Celsius - for example, 15/11 means 15°C temperature, 11°C dew point.

A spread of 4°C or less means conditions are ripe for fog formation. If you’re planning a morning departure and the overnight low is forecast to drop within 4 degrees of the dew point, check actual METARs before you leave for the airport. You may arrive to find the runway in fog.

Temperature and dew point also feed your density altitude calculation. Hot temperatures, high elevation, and humid air all reduce aircraft performance. Always calculate density altitude before takeoff. Don’t assume runway performance matches the field elevation on your sectional.

What Does the Altimeter Setting Tell Me?

The altimeter setting appears as a four-digit value in inches of mercury - for example, A2987 means 29.87 inHg. Set it before departure and update it en route.

Flying with an uncorrected altimeter in a changing pressure system means you are lower than your instrument shows. That gap matters near terrain and in instrument conditions. ATC provides current altimeter on request. ATIS gives it at your destination. Use both.

What Is in the Remarks Section?

Everything after RMK contains additional observed data that doesn’t fit the standard coded format. Do not skip it.

AO2 indicates the automated station has a precipitation discriminator - it can distinguish between rain and snow. That matters when temperatures are marginal and precipitation type changes the safety picture.

SLP followed by three digits is the sea-level pressure in hectopascals. Use it for precise altitude calculations and for reading synoptic weather patterns.

The remarks section also carries lightning observations, pressure tendency, variable ceiling information, and other phenomena the automated equipment detected. Some of the most operationally relevant information in a METAR lives in those three letters.

What Is a TAF and How Is It Different from a METAR?

The TAF (Terminal Aerodrome Forecast) is the National Weather Service forecast product for airports with instrument approaches and sufficient traffic volume. It uses the same sky condition and visibility codes as the METAR - once you can read a METAR, the elements are already familiar.

TAFs are issued four times daily: 0000Z, 0600Z, 1200Z, and 1800Z. They cover a 24- to 30-hour window depending on the airport. Always check the issuance time. A TAF can be up to six hours old if you’re briefing between issuance cycles. Stale weather data is not a minor inconvenience - it is a false picture of reality.

How Do I Read TAF Change Indicators?

The TAF is structured in time groups, each introduced by a change indicator:

FM (From) - A hard transition. Conditions change to what follows, beginning at the indicated Zulu time. Expect it around that time.

TEMPO (Temporarily) - Conditions expected to last less than one hour at a time, occurring within a stated window. TEMPO does not mean brief - it means the conditions come and go within that window. A TEMPO line showing low visibility and a broken ceiling deserves serious attention if your planned arrival overlaps that period.

BECMG (Becoming) - A gradual transition over a stated time window. Conditions shift progressively, not all at once.

PROB30 / PROB40 - A 30% or 40% probability of those conditions occurring. Some pilots read PROB40 and think “only forty percent.” Consider it differently: across four flights in that window, roughly two would encounter those conditions. Don’t dismiss probability lines when the conditions listed include thunderstorms or IMC.

How Do I Build a Complete Preflight Weather Briefing?

Work the briefing in a consistent sequence:

1. Departure airport - current METAR, then the TAF for your departure window
2. En route stations - METARs for reporting airports along your route; are any showing IMC between you and your destination?
3. Destination - current METAR, then the TAF through your full arrival window
4. Alternate - if the destination TAF shows deteriorating conditions before your arrival, pull METARs and TAFs for an alternate now, not after you’re airborne

If conditions look flyable at departure but the destination TAF shows a TEMPO block of IMC covering your arrival window, that TAF is telling you the airport may not be viable when you get there. Read it as a decision-making tool, not a curiosity.

The Airman Certification Standards require private pilot applicants to gather and interpret weather information, apply it to a specific flight plan, and demonstrate sound judgment about when weather makes a flight inadvisable. That means understanding what a METAR says and what it means for your airplane, your route, and your experience level that day.

Why Do Personal Minimums Matter?

The regulatory VFR ceiling minimum is not your personal ceiling minimum. The regulations define the floor of legality - not the threshold of sound judgment.

Build your personal minimums conservatively, especially early in your flying career. The ceiling the regulations technically permit is not the ceiling you should accept when you have 200 hours and are still developing your ability to read conditions in flight. Margin is not weakness. It is what experienced pilots call wisdom.

Read every METAR you can find, even on days you’re not flying. Decode them item by item until it becomes automatic. The day you really need it, you won’t have time to look up what BKN means.

Key Takeaways

• The ceiling is the lowest BKN or OVC layer only - FEW and SCT do not establish a ceiling
• A temperature/dew point spread of 4°C or less signals fog risk; check morning METARs before driving to the airport
• SPECI reports between routine hours signal changing conditions - multiple SPECIs mean something is actively developing
• TAF change indicators FM, TEMPO, BECMG, and PROB each describe a different type of transition; TEMPO requires particular attention when your arrival window overlaps it
• The weather brief is the only moment before engine start when you have access to the full picture - treat it as a decision-making tool, not a formality