Here's why:

* "Nimbus" means "rain cloud" in Latin.

* Nimbus clouds are thick, dark, and gray, indicating a high concentration of water droplets or ice crystals.

* These clouds often produce precipitation.

While "nimbus" refers to rain, it can also be used to describe other types of precipitation:

* Cumulonimbus: Thunderstorm clouds, associated with heavy rain, hail, lightning, and strong winds.

* Stratocumulus nimbus: Low-level clouds that can produce light rain or drizzle.

* Altostratus nimbus: Mid-level clouds that can produce light rain or snow.

So, the answer is nimbus clouds are associated with rain or snow, depending on the specific type of nimbus cloud.