METAR Basics for Charter and Corporate Pilots: Decoding Critical Weather Data

Why METARs Matter More Under Part 135 Than You Think

Ninety minutes before departure, a Part 135 crew pulls the latest METAR for their destination. The TAF predicted VFR conditions, but the METAR now shows BKN008 and 2SM in mist. The forecast and reality have diverged. What happens next depends entirely on how quickly and accurately that crew can decode the METAR — a standardized aviation weather report — and fold it into a go/no-go decision.

A METAR (Meteorological Aerodrome Report) is a standardized, real-time aviation weather observation from an airport. For charter and corporate pilots, it is far more than a training exercise. It is a regulatory requirement, a decision-making tool, and the final ground truth against which forecasts are validated. Forecast accuracy improves significantly within 24 hours of flight, making the METAR validation step in the final preflight window the single highest-value weather cross-check available.

Under 14 CFR Part 91.103, pilots must review all available weather data for IFR and cross-country flights. Part 135 operators face an additional layer of accountability: they must rely on official government weather sources — including METARs and TAFs — for aviation weather reports used in dispatch and flight planning. The flexibility that Part 91 pilots enjoy in selecting weather sources does not carry over to charter operations. Part 135 also imposes more restrictive ceiling and visibility minimums, demanding that pilots interpret METAR data with precision and operational discipline.

METARs serve as the final validation checkpoint in a layered weather assessment workflow: prog charts → TAFs → METARs → radar/satellite → PIREPs. This article delivers a professional-grade METAR decoding framework tailored for Part 135 and business aviation operators — with regulatory context, integration guidance, and the common traps that catch even experienced crews.

How to Read a METAR: Element-by-Element Breakdown

Whether you are building a METAR decoder for Part 135 charter pilots or refreshing your own rapid-interpretation skills for IFR flight planning, the structure is consistent and predictable. The METAR format follows ICAO Annex 3 standards for global consistency, adapted by the FAA for domestic use. FAA Order 7340.2P (updated through Change 2, dated November 27, 2025) governs the standardized contractions and phrasing you will encounter in every aviation weather report.

Here is the sample METAR we will decode element by element:

METAR KJFK 121856Z 31012G20KT 3SM +RA BKN015 OVC025 08/06 A2992 RMK AO2 RAB42 SLP134 P0012 T00830061

Station Identifier, Date, and Time

KJFK is the four-letter ICAO station identifier — in this case, John F. Kennedy International Airport. 121856Z indicates the 12th day of the month at 1856 Zulu (UTC). Always verify the observation time. A METAR that is 90 minutes old reflects conditions that may no longer exist. Stale data leads to poor decisions — confirm currency before acting on it.

Wind Direction, Speed, and Gusts

31012G20KT reports wind from 310 degrees true at 12 knots, gusting to 20 knots. The 8-knot gust spread signals mechanical turbulence potential on approach. For charter operations, cross-reference this against your aircraft’s demonstrated crosswind component and company SOP limits. Wind direction is always reported in degrees true — apply magnetic variation for runway alignment. A high gust spread during approach planning warrants briefing the crew on potential windshear and go-around criteria.

Visibility and Runway Visual Range

3SM indicates prevailing visibility of three statute miles. Part 135 operators commonly plan to a 2-mile visibility as a baseline minimum, though this varies by operator SOP, approach type, and terrain. When visibility drops below approach minimums, Runway Visual Range (RVR) values — reported in feet — become the controlling factor for precision approaches. If RVR is present in a METAR (e.g., R04R/2400FT), it takes precedence over prevailing visibility for determining approach authorization.

Present Weather Phenomena

+RA indicates heavy rain. The + prefix denotes heavy intensity; no prefix means moderate; – means light. Intensity qualifiers matter operationally — heavy rain affects braking action, visibility in precipitation, and engine performance. Common present weather phenomena codes include BR (mist), FG (fog), TS (thunderstorm), SN (snow), and FZRA (freezing rain). A frequent source of confusion: BR (mist) is reported when visibility is between 5/8 SM and 6 SM; FG (fog) applies when visibility drops below 5/8 SM. That distinction can define whether you are legal to depart or not.

Sky Condition and Determining Ceiling

BKN015 OVC025 reports a broken layer at 1,500 feet AGL and an overcast layer at 2,500 feet AGL. Cloud coverage descriptors — FEW (1–2 oktas), SCT (3–4 oktas), BKN (5–7 oktas), OVC (8 oktas) — indicate coverage density. The ceiling is the lowest BKN or OVC layer. FEW and SCT layers do not constitute a ceiling. In this METAR, the ceiling is 1,500 feet AGL (BKN015).

This distinction is critical for how to interpret METAR cloud layers and ceilings under Part 135 operations. Many operators use an 800-foot ceiling as a planning baseline, while some apply conservative margins in challenging terrain or mountainous environments. Misidentifying the ceiling layer is one of the most consequential METAR decoding errors a pilot can make.

Temperature, Dew Point, and Altimeter Setting

08/06 reports a temperature of 8°C and dew point of 6°C (an M prefix indicates negative values). The 2°C dew point spread is a red flag — when reading METAR temperature and dew point data, a spread of 2–3°C or less warns of imminent fog formation or further visibility deterioration. Monitor this trend across sequential METARs. A2992 is the altimeter setting: 29.92 inches of mercury. Accurate altimetry is non-negotiable for instrument approaches, and the altimeter setting directly affects density altitude calculations relevant to aircraft performance.

Remarks Section (RMK)

RMK AO2 RAB42 SLP134 P0012 T00830061 — the remarks section is often overlooked but contains operationally valuable data. AO2 identifies an automated station with a precipitation discriminator. RAB42 indicates rain began at 42 minutes past the hour. SLP134 is sea-level pressure (1013.4 hPa). T00830061 provides temperature and dew point in tenths of a degree for more precise trend analysis. FAA Order 7340.2P standardizes these remarks contractions — familiarity with them strengthens your ability to extract trend data that the main body of the METAR does not capture.

METAR vs. TAF: Understanding the Critical Difference

The most persistent misconception in preflight weather planning: treating a METAR as a forecast. A METAR reports current observed conditions at a specific moment. A Terminal Aerodrome Forecast (TAF) predicts conditions 24 to 30 hours ahead. The METAR vs. TAF differences for pilots are fundamental — one is ground truth, the other is a model-based projection.

Consider how they function together. The TAF sets expectations during initial flight planning. The METAR, pulled in the final 1–2 hour preflight window, validates those expectations against observed reality. When the two aviation weather products agree, confidence in the weather picture increases. When they diverge, the crew faces a decision point that demands immediate attention.

Under Part 135, both official METARs and TAFs are required for weather decisions — neither alone is sufficient. The TAF without a METAR leaves you planning against a prediction with no real-world confirmation. The METAR without a TAF gives you a snapshot with no forward-looking context. Effective preflight weather planning depends on the cross-check between the two, especially as departure time approaches and forecast accuracy improves.

Integrating METARs into Your Weather Workflow

Decoding a METAR accurately is necessary. Integrating it into a layered weather assessment is what separates a competent pilot from an operationally excellent one. Here is the decision framework business aviation professionals should follow:

1. Long-range prog charts (24–36 hours out): Establish the big-picture synoptic pattern — frontal positions, pressure systems, areas of expected IFR conditions. This sets the strategic planning context.
2. TAFs as the forecast baseline: Pull TAFs for departure, destination, and alternates. Identify forecast windows where ceiling and visibility may approach minimums.
3. METAR validation (1–2 hours preflight): Cross-check the latest METAR against the TAF. Flag any discrepancies — conditions better or worse than forecast. This is the highest-value step in the workflow.
4. Radar summaries for precipitation confirmation: Radar updates hourly and provides echo tops and cell movement data. Critical distinction: radar shows precipitation, not clouds. Use it to confirm what the METAR’s present weather group is reporting.
5. Satellite imagery for cloud and ceiling verification: Satellite is the complementary tool to radar — it shows cloud coverage, tops, and movement. If the METAR reports BKN015, satellite imagery confirms the extent and trend of that layer.
6. PIREPs for real-world confirmation: Pilot weather reports provide ground truth from aircraft operating in the airspace you are about to enter. Turbulence, icing, and ceiling reports from other crews are irreplaceable.

A critical operational point: METAR absence in remote or data-sparse areas does not mean clear weather. When destination METARs are unavailable, compensate with model data, PIREPs, and satellite imagery, and apply conservative planning margins.

When METARs and TAFs Disagree

Scenario: the TAF for your destination calls for SCT025 and 6SM. You pull the METAR 90 minutes before departure and it shows BKN008 2SM BR. The forecast and observed conditions have diverged significantly. Which product takes priority? The METAR — it reflects observed reality.

When this discrepancy arises, request an updated ATIS or contact dispatch for a revised forecast. Evaluate whether the trend is improving or deteriorating by reviewing sequential METARs. Under Part 135, conservative interpretation is the standard — if the METAR shows conditions at or near minimums and the TAF did not predict it, treat this as a trigger for a full go/no-go reassessment. Do not assume the TAF will “catch up” to reality.

Part 135 METAR Minimums and Regulatory Compliance

METAR decoding for Part 135 dispatch decisions carries regulatory weight that Part 91 operations do not share. Under 14 CFR Part 135, charter operators must use official government weather sources — METARs and TAFs — and operate within ceiling and visibility minimums that are more restrictive than those available to Part 91 private flights. Third-party weather apps and non-official sources do not satisfy this requirement.

Common Part 135 planning baselines include an 800-foot ceiling and 2 statute miles visibility, though actual minimums vary significantly by operator, approach type (precision vs. non-precision), airport environment, and terrain. PIC discretion applies within the framework of company SOPs — this is not a rigid, one-size-fits-all mandate. Some operators set higher IFR minimums for specific routes, crew experience levels, or mountainous terrain.

14 CFR Part 91.103 mandates preflight action including a weather review for IFR and cross-country flights. Part 135 operations layer additional requirements on top of this baseline. Pilots operating under Part 135 should know their company SOPs and the applicable FARs — not as general guidelines, but as the operational boundaries within which every go/no-go decision must be made.

For comprehensive Part 135 regulatory and weather training, see CTS’s FAR Part 135 Training packages.

Common METAR Mistakes Even Experienced Pilots Make

Even with instrument ratings and thousands of hours, these errors persist. Use this as a quick-reference reality check for your own METAR training habits:

• Confusing METARs with TAFs. A METAR is an observation of current conditions. A TAF is a forecast. They serve different functions in the preflight workflow, and substituting one for the other leads to flawed decision-making.
• Misidentifying the ceiling. The ceiling is the lowest BKN or OVC layer, period. FEW and SCT layers do not constitute a ceiling. Reporting SCT012 does not mean you have a 1,200-foot ceiling.
• Assuming radar shows clouds. Radar shows precipitation — not cloud coverage. If you need to assess ceilings or cloud layers beyond what the METAR reports, satellite imagery is the correct tool.
• Treating METAR absence as clear weather. In data-sparse or remote areas, no METAR does not equal no weather. Compensate with models, satellite, and PIREPs, and apply conservative margins.
• Applying Part 91 flexibility under Part 135. Part 91 allows broader discretion in weather source selection and personal minimums. Part 135 does not. Operating under charter authority with a Part 91 mindset is a compliance risk and a safety risk.

Frequently Asked Questions About METARs

What does a METAR tell you about current weather conditions?
A METAR reports current observed conditions at an airport, including wind direction and speed, prevailing visibility, present weather phenomena (rain, fog, snow), sky condition and cloud layers, temperature, dew point, and altimeter setting. It is a standardized aviation weather snapshot of conditions at the time of observation — not a forecast.

How do you determine ceiling from a METAR report?
The ceiling is the lowest broken (BKN) or overcast (OVC) cloud layer, reported in hundreds of feet AGL. FEW and scattered (SCT) layers do not count as a ceiling. In the METAR example BKN015 OVC025, the ceiling is 1,500 feet AGL.

What is the difference between a METAR and a TAF?
A METAR is an observation of current conditions at a specific time. A TAF is a Terminal Aerodrome Forecast that predicts weather conditions 24 to 30 hours ahead. Under Part 135, both are required for preflight weather planning — the METAR validates what the TAF predicted.

What METAR minimums are required for Part 135 charter operations?
Part 135 commonly uses an 800-foot ceiling and 2 statute miles visibility as a planning baseline, but actual minimums vary by operator SOPs, approach type, terrain, and crew qualifications. Always reference your company’s operations specifications and standard operating procedures for applicable minimums.

How often are METARs issued and how current is the data?
METARs are typically issued hourly, approximately 55 minutes past the hour. Special observations (SPECI) are issued when conditions change rapidly — such as significant shifts in visibility, ceiling, wind, or the onset of thunderstorms. Always check the observation time to confirm the METAR reflects current conditions.

Sharpen Your METAR Skills for Charter and Corporate Operations

METAR proficiency is not optional for Part 135 and corporate pilots — it is a regulatory requirement and a core professional skill. Use METARs as the final real-world aviation weather validation against TAFs in the last 1–2 hours before departure. Integrate them into a layered weather assessment that includes prog charts, radar, satellite, and PIREPs. Recognize when the data tells you to stop and reassess.

While this article provides a professional-grade reference framework, building true rapid-decoding proficiency requires repetition and scenario-based practice — exactly what structured e-learning delivers. For interactive, scenario-driven METAR and weather training designed for Part 135 checkrides, dispatch coordination, and daily operations, explore CTS’s METAR and TAF Online Aviation Training.