Cloud Cover
Elementary School
Definition
The fraction of the sky covered by clouds at a given time, used to describe and predict weather. Meteorologists estimate cloud cover because it affects temperature, the chance of precipitation, and how much sunlight reaches the ground.
Worked examples
A sky with scattered cumulus clouds covering about 3/8 of the visible sky has \(37.5\%\) cloud cover.
Cloud cover is the fraction or percentage of sky obscured by clouds when looking up.
On a clear night with 0% cloud cover, temperatures drop quickly because heat escapes to space; with 100% cloud cover, clouds trap heat and keep it warmer.
Cloud cover directly affects nighttime cooling and daytime heating by blocking or trapping radiation.
Common mistakes
- Cloud cover only matters for whether it will rain. → Cloud cover affects temperature, sunlight reaching the ground, and precipitation chance. Clouds influence weather in many ways beyond just rain—they regulate heat loss and solar heating.
- A few large clouds mean high cloud cover. → Cloud cover is the fraction of the entire sky covered, not the number of clouds. A few large clouds might cover only 20% of the sky; many small clouds might cover 80%.
- Cloud cover is measured in meters or kilometers. → Cloud cover is measured as a fraction, percentage, or in oktas (eighths of sky). Cloud cover describes area of sky covered, not height or distance.
Where you'll use it next
You'll use cloud cover when studying weather patterns, climate systems, and energy balance in Earth science. It's key for understanding temperature forecasts, solar energy availability, and the greenhouse effect.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026