Sky cover
Also called cloud cover circle, oktas, sky circle
Station model. What an observer recorded, not a weather-app forecast.
Present weather and station modelsSky cover meaning
Sky cover is the fill of the circle on a station model, an observation of how much sky was covered. It is not a partly cloudy forecast icon.
At a glance
- System
- NOAA station model
- Used for
- Observed cloud cover
- Not the same as
- A partly cloudy or overcast forecast icon
The filled circle on a station model. More ink means more of the sky was covered.
The name. Sky cover is the fill of the station circle. It is an observed fraction of the dome, not a picture of a cloud.
Where it comes from
Weather Prediction Center plots make the station circle itself the sky cover. More of the circle filled means more cloud was observed. This drawing is half filled so the idea is visible at a small size. It is a middle step, not a claim that every service uses the same fractions. A forecast of partly cloudy or overcast is a picture and a word for a future period. The circle is a report.
The line drawing is original to this cabinet. It is not an agency logo, a vendor icon, or the emoji for the same idea.
Weather
What it means
The observer, or the sensor, judged the dome. An empty circle is a clear observation. A filled circle is a covered one. An obscured sky, when fog or snow hides the cloud base, is a further convention on full plots. This page does not invent a private set of eighths. It points at the circle and tells you to read the fill before you read any cloud clip-art nearby.
Variants
Clear to covered
Empty, partly filled, and filled are the readable steps. Forecast words such as few, scattered, broken, and overcast are a different vocabulary, used in written observations and in apps. Do not assume one fill equals one of those words unless the plot’s legend says so.
Questions
What does the circle on a station model mean?
Its fill is the sky cover. The Weather Prediction Center uses that circle for how much of the sky was covered at observation time.
Is a half-filled circle partly cloudy?
Only in the loose sense that about half the dome was covered. Partly cloudy on a phone is a forecast icon. The circle is a plot.
Near this
- Station modelThe whole observation plot. Sky in the circle, wind on the barb, weather only if something is falling or the air is thick.
- Cloudy and overcastForecast icons for a covered sky. Cloudy and overcast are not the same row, and neither is rain.
- Partly cloudyA forecast icon for sun and cloud together. Not overcast, and not a station-model sky circle.
- Clear skyA forecast icon for an expected open sky. Not the alchemical sun, and not a clear night.
Sources
Named when the entry depends on a text, a date, or a standard. Catalog numbers are not invented.
Your margin
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symbol.wiki, edited as Sigilla. Last reviewed 18 October 2026. A reading of public tradition, not a ruling.