What type of cloud is generally dark and associated with precipitation?

Cumulonimbus clouds are characterized by their towering, vertical structure and are often associated with significant weather events, including heavy rain, thunderstorms, and even severe weather phenomena like hail and tornadoes. These clouds typically have a dense, dark appearance, particularly when they are thick and loaded with moisture. The intensity of the precipitation they produce can range from light rain to severe downpours, making them the clouds most commonly linked to stormy weather.

In contrast, cumulus clouds are more puffy and white, often indicating fair weather rather than precipitation. Stratus clouds tend to cover the sky in a uniform layer and produce light rain or drizzle rather than heavy precipitation. Altocumulus clouds, while they can indicate some moisture in the atmosphere, do not usually lead to significant rainfall and are more fluffy or cotton-like than dark and stormy. Thus, the distinct characteristics of cumulonimbus clouds clearly identify them as the type associated with darker conditions and substantial precipitation.