Why are rain and storm clouds visually darker than regular clouds?

Question

I’ve seen a previous answer stating that different clouds scatter sunlight differently, but what causes these clouds in particular to darken?

In: 11

Answer 1

They are much taller and denser than normal clouds, so the light has more to pass through before reaching your eyes, thus appearing darker.

Answer 2

Rain forms round particles in the air called condensation nuclei, there is a very large amount (tons) of water and dust in rain clouds so they are much darker than other clouds.