Clouds look a little weird when you're looking at them through any glass or glass pane or water.

Without glass:

Looking at it through glass:

Steps to reproduce:

1. Create a New world, Enter world with a PBR resource pack enabled that supports water & glass properly, such as Nvidias Crystal palace resource pack.
2. Place some Glass
3. Look at Clouds through glass

Expected results:
Cloud looks similar to if It's not seen through glass.

Observed results:
Weird dots appear.

I also confirmed It happens with any fog configuration that affects clouds.
Also: Glass texture should be transparent enough so you can see through it properly.

Other notes:
It seems It's a general thing about Refraction, as the same bug happens when you look at clouds through water, here is screenshots of bug happening with Water:

Zoomed in:

Another example of water:

Steps to reproduce it for water:

1. Create a New world, Enter world with a PBR resource pack enabled that supports water & glass properly, such as Nvidias Crystal palace resource pack.
2. Go under water
3. Look at clouds
4. You'll see the same bug that happens with Glass/glass pane.