American Meteorological Society Certification (AMS) Practice

Stratus clouds are characterized by their uniform, grayish appearance, typically covering the entire sky like a thick blanket. They form in stable atmospheric conditions and often result in overcast weather. Stratus clouds can lead to light precipitation, such as drizzle or light rain, and are associated with prolonged periods of cloudiness.

In contrast, cumulus clouds are puffy and fluffy, often appearing in a more unstable atmosphere, and typically indicate fair weather when they are small and well-defined. Cirrus clouds are thin and wispy, generally positioned at high altitudes, and are not uniform in color or texture. Nimbus clouds refer to a type of cloud that produces precipitation; however, they are often associated with specific forms, such as nimbostratus or cumulonimbus, rather than being a standalone classification. Therefore, the characteristics of stratus clouds align perfectly with the description in the question.