Chapter 3b: Effects of Weather on Small Unmanned Aircraft Performance  Ceiling Visibility For aviation purposes, a ceiling is the lowest layer of clouds reported as being broken or overcast, or  the vertical visibility into an obscuration like fog or haze. Clouds are reported as broken when five- eighths to seven-eighths of the sky is covered with clouds. Overcast means the entire sky is covered  with clouds. Current ceiling information is reported by the aviation routine weather report (METAR)  and automated weather stations of various types. Closely related to cloud cover and reported ceilings is visibility information. Visibility refers to the  greatest horizontal distance at which prominent objects can be viewed with the naked eye. Current  visibility is also reported in METAR and other aviation weather reports, as well as by automated  weather systems. Visibility information, as predicted by meteorologists, is available for a pilot during a  preflight weather briefing. Remote Pilot – Small Unmanned Aircraft Systems Study Guide  28 