CAVOK

Definition

CAVOK is an abbreviation used in METAR and ATIS reports to indicate ideal weather conditions for aviation. It stands for "Ceiling and Visibility OK" and replaces a longer list of weather elements when all key conditions meet favorable thresholds. When CAVOK is reported, pilots can assume excellent flight visibility and no significant weather phenomena that would affect visual flight or standard instrument operations.

Criteria for CAVOK

All of the following conditions must be true simultaneously:

  • Visibility is 10 km (9999) or more
  • No significant weather phenomena are present or forecast (e.g., no rain, snow, fog, thunderstorm, etc.)
  • No clouds below 5000 ft AGL or below the highest minimum sector altitude (MSA), whichever is higher
  • No cumulonimbus (CB) or towering cumulus (TCU) clouds
  • No weather significant to aviation in the vicinity of the aerodrome

If any of these conditions are not met, CAVOK cannot be used and specific weather elements will be listed individually.

Where CAVOK Appears

  • In METAR reports (e.g., LOWG 101350Z 27005KT CAVOK 16/07 Q1017 NOSIG)
  • In ATIS broadcasts (e.g., “Wien ATIS, Information Bravo, time 1200 Zulu, wind calm, CAVOK, temperature 15…”)

Interpreting CAVOK

Code Meaning
CAVOK Visibility ≥10 km, no significant weather, no low clouds
9999 (in METAR) Same visibility as CAVOK, but may include clouds or weather phenomena

Note: CAVOK replaces:

  • Visibility line
  • Weather phenomena line
  • Cloud coverage line

Benefits for Pilots

  • ✅ Quickly assess excellent VFR conditions
  • ✅ Save time in reading METAR/ATIS
  • ✅ Know that no weather-related restrictions exist below 5000 ft or MSA
  • ✅ Safe for basic VFR training, departures, and approaches

When CAVOK Cannot Be Used

  • ❌ If clouds are present below 5000 ft AGL or below MSA
  • ❌ If visibility is less than 10 km
  • ❌ If CB/TCU clouds are observed
  • ❌ If weather such as rain, fog, thunderstorm, or haze is present

Example METAR with CAVOK

 LOWW 081250Z 27008KT CAVOK 19/11 Q1016 NOSIG

Translated:

  • Vienna Airport, observed at 12:50 UTC
  • Wind from 270° at 8 kt
  • CAVOK: visibility ≥10 km, no significant weather, no CB or low cloud
  • Temperature: 19°C, dew point 11°C
  • Pressure: 1016 hPa
  • No significant change expected (NOSIG)

Useful Phraseology

 “Copied ATIS Information Alpha, wind calm, CAVOK.” “CAVOK conditions at destination, planning VFR arrival.”