Here's why:

* Nimbus means "rain cloud" in Latin.

* These clouds are thick, dark, and gray, indicating they are full of water droplets or ice crystals.

* The water droplets or ice crystals are heavy enough to fall as rain, snow, sleet, or hail.

Therefore, any weather associated with nimbus clouds will likely involve some form of precipitation.

Specific types of nimbus clouds:

* Cumulonimbus: These are towering, thunderhead clouds that bring heavy rain, thunder, lightning, and sometimes hail or tornadoes.

* Nimbostratus: These are dark, gray, layered clouds that produce steady rain or snow over a wide area.

So, when you see nimbus clouds, be prepared for rain!