“Why do clouds appear in so many colors?” – Jean

One of my favorite things about clouds is how unique they are in appearance — whether in shape, size or color.

But, let's start with how they get to be their most familiar color: white.

Clouds are made up of tiny water droplets or ice crystals that are similar in size to the wavelengths of sunlight. This means when they scatter the light, they scatter all the colors on the visible spectrum equally (remember ROYGBIV?), which our eyes perceive as white.

However, when clouds get thicker, more of the sunlight can get blocked from passing through, which makes them appear more gray in nature.

When the sun starts to go down, the story changes.

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During sunrise and sunset, the sun is low in the sky, creating a longer path for the light to travel.

As the sun’s rays move along the path, the shorter wavelengths get scattered out first — leaving behind the longer wavelengths: red, orange and yellow.

And these colors are what is then reflected in the clouds, giving us some of the most breathtaking sunset experiences.

But I would be remiss in answering this question without addressing one of the weirder cloud colors we see from time to time: green.

The eerie green color we get asked about all the time is associated with severe weather, and for good reason.

Moisture is one of the major ingredients needed for a storm to become severe. This green or blue-ish hue is an indicator that the clouds are holding an immense amount of moisture and ice crystals, sometimes even hail. 

The raindrops in these storm clouds tend to absorb warmer colors of light while letting the blues bounce around. Add in the setting sun, around when most severe weather occurs, and the combination of the yellow light and blue gives you that unsettling green hue.

Have your own favorite cloud photos? I’d love to see them. Drop them below!

Caitlin Kaiser graduated from the Georgia Institute of Technology with both an undergraduate and graduate degree in Earth and Atmospheric Sciences before starting her career as a digital meteorologist with weather.com.