Definition
The height above the ground or water of the lowest layer of clouds reported as broken or overcast, or the vertical visibility into an obscuration such as fog or smoke. Ceiling is reported in feet above ground level (AGL) and appears in weather products like METARs, TAFs, and Area Forecasts as the abbreviation CIG.
Plain English
How high above the ground the lowest mostly-cloudy or fully-cloudy cloud layer sits. If the sky is hidden by something like fog, the ceiling is how far up you can see before the view is blocked.
Context Anchor
Seen in aviation weather forecasts and reports when cloud height is important for flight planning and go/no-go decisions.
Derivation
From the everyday word 'ceiling,' meaning the upper surface of a room. In aviation, the sky becomes the 'room' and the cloud layer becomes its ceiling — the height beyond which the pilot effectively cannot go visually.
Why Pilots Care
A low ceiling determines whether visual flight is legal or instrument procedures become necessary.
Grounding Statement
If most of the sky over an airport is covered by clouds starting at 800 feet above the ground, the ceiling is 800 feet.
Intuition Check
Do not read ceiling as just any cloud height. In aviation weather, it means the lowest layer that mostly covers the sky, or a layer like fog or smoke that hides the sky.
Example Sentence 1
The Area Forecast showed CIG 1,500 broken across the route, so the VFR pilot decided to delay departure.
Example Sentence 2
With the reported ceiling at 2500 feet we remained VFR and continued to the destination.