CAVOK (pronounced "kav-oh-kay") is a METAR shorthand term meaning "Ceiling And Visibility OK." Controllers and meteorologists use it to indicate that visibility, cloud cover, and weather all meet specific thresholds, allowing a single abbreviation to replace several separate report fields.
How It Works#
A METAR is a routine weather observation report issued at airports worldwide. Normally, it lists visibility, present weather, and cloud layers in separate fields. When conditions meet all CAVOK criteria, those fields collapse into one word.
ICAO defines CAVOK as requiring three conditions to be true at the same time. Visibility must be at least 10 km. No cumulonimbus (CB) or towering cumulus (TCU) clouds can be present, and no other clouds can exist below 1,500 m (approximately 5,000 ft) above the aerodrome elevation. There must also be no significant weather, such as precipitation, thunderstorms, or shallow fog.
The threshold of 1,500 m matters because it aligns with the standard obstacle clearance height used in instrument approach procedures. A sky clear of clouds below that level gives pilots meaningful separation from terrain and obstructions.
Note that CAVOK is an ICAO standard and appears in reports from most international airports. The FAA uses it in received international METARs but does not generate CAVOK in U.S. domestic reports. U.S. stations instead report each field separately, or use "SKC" (sky clear) and "CLR" (clear below 12,000 ft).
Example in Aviation#
A pilot preparing to fly from Amsterdam Schiphol (EHAM) to Paris Charles de Gaulle (LFPG) pulls up the destination METAR during preflight planning. The report reads: LFPG 141230Z 27008KT 9999 CAVOK 22/10 Q1018. The CAVOK tells her that visibility exceeds 10 km, no clouds are present below 5,000 ft, and no significant weather affects the field. She can expect a smooth visual approach with no weather-related complications at arrival.
Why It Matters#
For pilots, CAVOK is a quick, reliable signal that conditions are well above most minimums. Reading a single term instead of parsing multiple weather fields speeds up preflight weather scans and reduces workload, especially when reviewing several alternates at once.
For student pilots learning to decode METARs, recognizing CAVOK early saves time and builds situational awareness. Understanding what the term requires also teaches what it excludes: CAVOK says nothing about wind, temperature, or pressure, so those fields always appear alongside it in the report.
Key Takeaways#
- CAVOK replaces the visibility, weather, and cloud fields in a METAR when all thresholds are met.
- Visibility must reach at least 10 km for CAVOK to apply.
- No clouds are permitted below 1,500 m (approximately 5,000 ft) above aerodrome elevation.
- No significant weather (precipitation, thunderstorms, fog) can be present.
- CAVOK is an ICAO standard and does not appear in U.S. domestic METAR reports.