Why are rain clouds gray and also why is it that the darker they are the more severe the storm is?

Question

Why are rain clouds gray and also why is it that the darker they are the more severe the storm is?

Answer 1

Clouds are made up of tiny water droplets or ice crystals, usually a mixture of both. The water and ice scatter all light, making clouds appear white. If the clouds get thick enough or high enough all the light above does not make it through, hence the gray or dark look. Also, if there are lots of other clouds around, their shadow can add to the gray or multicolored gray appearance.

Answer 2

Clouds are gray because they equally scatter visible light at all wavelengths. Darker clouds signify higher tops. That's generally the case with a cumulonimbus cloud. Since clouds reflect a portion of incoming solar radiation as well, there is less light reaching the base of cloud and the surface of the Earth.

Answer 3

Light is white, so when clouds are thin, you can see it, but if they get too thick, the light can't get through.