Why Clouds Appear Black During Rain?

White is how our eyes perceive all wavelengths of sunlight mixed together. When it's about to rain, clouds darken because the water vapor is clumping together into raindrops, leaving larger spaces between drops of water. Less light is reflected. The rain cloud appears black or gray.

Why do rain clouds get dark?

But why are rain clouds so dark? ... That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the more light it scatters, resulting in less light penetrating all the way through it.

What does it mean when clouds are black?

A: Very dark looking or black clouds are probably those that contain a lot of rain in them and part of a thunderstorm, McRoberts adds. "In general, the severity of a storm is related to cloud height, which is why dark clouds are usually an indicator of bad weather.