While overcast and cloudy weather conditions both involve clouds in the sky, there is an important distinction between the two terms. Let’s take a closer look at what defines overcast weather and what defines cloudy weather.
Overcast Weather Overcast refers to dense, complete, or nearly complete cloud cover where clouds obscure most or all of the sky and block out direct sunlight. When meteorologists describe conditions as overcast, it means there is a solid or nearly solid layer of gray clouds blanketing the sky. The percentage of sky covered is estimated to be over 95%. On an overcast day, no distinct or individual clouds can typically be seen - just a uniform, gray blanket from horizon to horizon. Diffuse, dim light permeates from the clouds but direct sunrays are unable to penetrate through the thick overcast cloud layer.
Cloudy Weather In contrast, cloudy weather incorporates clouds but does not imply 100% or near 100% sky cover. There are usually gaps between individual clouds or cloud clusters that allow some patches of clear sky and direct sunlight to peek through. The percentage of sky obscured is typically less than 80%. Discrete clouds of various sizes and shapes are distinguishable, rather than a continuous blanket. On a cloudy day, sunlight is intermittent as clouds pass over the sun, creating alternating periods of brightness and shade. Visibility of the ground is generally better than during overwhelmingly overcast conditions.
In summary, weather is considered overcast when dense, homogeneous cloud cover blocks out most or all available sunlight. Cloudy weather denotes substantial cloud amount with breaks that allow sun and patches of clear sky to be directly viewed between individual clouds or groups of clouds. Determining whether conditions are overcast versus just cloudy comes down to estimated sky cover percentage and ability to see distinct, separate clouds.