I want to mention this one.
When you see bright white clouds on a nice day, this color bright white tells you that your area is clean.
If you see one that has gray or sometimes little tan on the clouds, then you have a problem with your town because your town produces a lot of dirty air that we really cannot see in the air.
The only way is for you to see at the bottom of the cloud where it absorbs the "smoke." The bright ones are on the top of the clouds have nothing to do with the clean or dirty.
A lousy day is hard for us to observe the clouds because the clouds increased mass of the form. Probably, they are carrying some water in them.
Actually, the dirty clouds move into the ocean. The salt air take the dirty particles down into the ocean. It's part of the nature cycle.
