They are the highest clouds. They are made of tiny ice crystals, not water droplets. They can be seen on clear sunny days. Cumulus nimbus clouds are really cumulus clouds that mass together and keep growing until they become full of so much moisture that they turn dark and heavy. They are just above stratus clouds and they often bring heavy rains and thunder and lightning.
Stratus clouds are the lowest clouds.
These clouds can stretch for hundreds of miles. Drizzle or snow flurries can come from them. Cloud Activities Keep track of the clouds every day for one week. Look at the sky in the morning and in the late afternoon. Go outside and observe clouds.