Cumulonimbus Stormy Weather 

Just like you see a cumulus cloud and know it means fair weather, cumulonimbus mean the weather is stormy. (Ironically, it is the very act of these harmless fair weather cumulus clouds overdeveloping that creates cumulonimbus.) Any time you see a cumulonimbus on the horizon, you can be sure that dangerous severe weather—such as short periods of heavy rain, lightning, hail, and possibly tornadoes—isn't far off. 

• Precipitation Cloud: Yes, often with intense rain and severe weather.