CAVOK

A term appearing in aeronautical weather reports when visibility is optimal and does not pose a notable issue for pilots. It is the acronym for Ceiling And Visibility OK. It replaces the groups - in coded language - corresponding to that variable when, simultaneously, the aforementioned visibility is greater than or equal to 10 km, there is an absence of clouds below 1500 m or a reference altitude (different for each airport or aerodrome), and cumulonimbus, towering cumulus (vertically well-developed cumulus), or significant weather phenomena are also neither observed nor forecast. It habitually appears written in uppercase (CAVOK).