As an aid to weather forecasting to determine cloudiness The National Weather Service uses these terms to define these sky conditions:
|Sky Condition||Opaque Cloud Coverage|
|Clear/Sunny||1/8 or less|
|Mostly Clear/Mostly Sunny||1/8 to 3/8|
|Partly Cloudy/Partly Sunny||3/8 to 5/8|
|Mostly Cloudy||5/8 to 7/8|
|Cloudy||7/8 to 8/8|
For more weather terms see Forecast Terms at the National Weather Service.