Plain English Meaning

CLR on a METAR means an automated weather station did not detect any clouds below 12,000 feet above the ground. Higher clouds may still exist — the machine simply cannot see them.

Full Definition

In a METAR sky condition group, CLR indicates that no clouds were detected below 12,000 feet AGL by an automated weather observing station. It is reported only by automated stations (ASOS/AWOS) and means the automated sensor found no clouds within its detection range; it does not certify the sky is clear above 12,000 feet.

Context Anchor

Seen in the sky condition section of a METAR, where cloud cover is reported.

Derivation

CLR is just a shortened form of 'clear.' METARs use compact codes to keep short enough to quickly teletype and .