Cloud Color

Have you ever wondered why some clouds appear dark, and others appear white? Do dark clouds indicate that an ominous storm is approaching? Well, let’s explore this topic!

Cloud color is not necessarily directly related to the severity or intensity of a storm. In most cases, the sunlight actually plays the pivotal role in cloud cover.

Take the following picture for example. Notice the sun’s rays illuminating the clouds, making them appear white.

Or look at this picture taken by myself on April 3, 2012 in the Great Smoky Mountains National Park. The sun is directly overhead, shining on the towering cumulus clouds in the distance. This makes them appear bright white.

However, there are cases when the clouds look very ominous and dark. A majority of time this is cause by the clouds blocking out the sunlight, causing a shadow to fall on the rest of the cloud. Take the below photo as an example. The clouds appear dark because of the shadow that’s being cast on them. The clouds themselves are not dangerous, despite their dark appearance.

Notice the same effect in the following picture. The sun is beginning to set behind the clouds and associated precipitation. This casts a shadow on the clouds closest to me, making them appear dark and menacing, while in reality it’s just a summer rain shower. This actually produced a photogenic double rainbow behind me.

So what exactly makes clouds dense enough to block out the sunlight? Well, all clouds are white due to their formation. However, as the cloud grows and more moisture particles accumulate, the cloud becomes dense enough to block out the sunlight. This is how the shadow is cast.

Sunsets can also make for some spectacular cloud colors. I will get more into the science behind that tomorrow. However, as a teaser here’s a picture of some mammatus clouds at sunset in Draffenville, KY. I took this photo on August 3, 2011.