What is the operational meaning of the sky condition code SKC or CLR in a METAR?

SKC and CLR both report an absence of cloud, and the difference between them is the observing method rather than the sky. SKC is used in a human observation and means the observer saw no clouds at all. CLR appears in automated reports and means the station's sensor detected no clouds below 12,000 feet — a qualification worth remembering, since cloud above that height would go unreported. In either case there is no cloud for the Part 107 clearance requirement to apply to, so the operation is bounded by visibility, the 400-foot ceiling and the other operating rules rather than by cloud. Two habits keep this from becoming a trap. The report is an observation at that station at that time, so conditions can differ at a site some distance away and can develop within the hour. And CLR's 12,000-foot limitation means an automated clear report is a statement about the low altitudes, which is all a remote pilot needs but is not the same as a cloudless sky.

SKC and CLR both report no clouds detected, so there is no cloud for the clearance requirement to apply to at the time and place of the observation.

SKC indicates clear skies in a human observation; CLR indicates no clouds detected below 12,000 feet in an automated report. Neither triggers the Part 107 cloud clearance requirement at the observation time and location.

SKC Human, CLR Automated below twelve thousand. Either way, no cloud to stay clear of.

A clear report is still a point observation. Conditions at a site some distance away, or an hour later, may differ.

• •Reading CLR as meaning no cloud at any altitude
• •Treating a clear report as valid for a distant site or a later hour
• •Confusing the codes with an unreported or unmeasured sky condition