Cloud Cover
Learn what cloud-cover percentages mean and how clouds influence sunlight, temperature and visibility.
What cloud cover describes
Cloud cover estimates how much of the sky is occupied by clouds from a location. A low percentage generally means more open sky, while a high percentage indicates that much of the sky is cloudy. It does not directly say whether rain is falling.
Clouds can change temperature
During daylight, clouds can reduce incoming sunlight and limit surface heating. At night, cloud can reduce heat loss from the surface. The effect depends on cloud type, thickness, time of day and the wider atmosphere.
Cloud cover is not precipitation
A mostly cloudy sky can remain dry, while a short shower can occur under a changing sky. For rain decisions, use precipitation probability, precipitation amount when available, and radar or official warnings rather than cloud percentage alone.
Why observations differ
Clouds form, move and dissipate continuously. A forecast represents an expected condition for a particular time and place, while a nearby observer may see something different. Mountains and coastlines can increase these differences.
Planning with cloud cover
Cloud cover is useful for judging likely sunshine and changes in daytime heating, but it works best alongside temperature, wind, precipitation and visibility.
Worked example: the same percentage, different light
Imagine two forecasts showing 80% cloud cover. In the first, thin high cloud covers much of the sky; in the second, a thick low layer blocks most direct sunlight. The percentage alone cannot tell a photographer which scene will produce soft light, a visible sunset or a view of distant hills.
Before an outdoor shoot, pair the cloud estimate with the hourly trend, visibility and actual sky conditions. If only total cloud cover is available, acknowledge the missing information about layer height and thickness rather than inventing it from the number.
Does 25% cloud mean 45 minutes of sunshine per hour?
No. Cloud coverage is a spatial fraction, not a clock. Clouds might remain away from the sun, pass repeatedly across it or cover it for most of the hour. You cannot convert the percentage directly into sunshine duration.
Why does the view from my window differ?
A window shows part of the sky, often with buildings obscuring the horizon. A model estimates conditions across a grid area. Neither is the same as an unobstructed human assessment of the entire sky. Our cloud-cover tile uses modeled data.
Cloud amount, height and type
The Met Office explanation of cloud observations distinguishes these properties. Use our precipitation guide for rain decisions and temperature guide for changes through the day.
Editorial note: Weather information varies by location, observation source and update time. This article is for general education and everyday planning. For severe weather or safety-critical decisions, follow the relevant official meteorological and emergency authorities.