Originally published: 2007 | Last updated: 06-08-25 – This article now provides clearer explanations and examples about the science behind cloud colors, ranging from dramatic and stormy to awe-inspiring.
Like most of us, meteorologists recognize that towering, dark gray clouds usually signal that rain is on the way, while soft, white, puffy clouds often mean sunshine and fair weather. But what many of us don’t know is why clouds appear in different colors—and what those colors can tell us about the sky above.
Why Are Clouds White?
Clouds form when tiny water droplets condense around particles in the atmosphere. These droplets are actually transparent, but they scatter sunlight in all directions. Because sunlight is made up of all colors of visible light, this scattering gives clouds their familiar pearly white appearance.
Why Do Some Clouds Look Dark?
As clouds grow thicker and more saturated with moisture, the spaces between droplets widen, allowing light to travel deeper inside the cloud. Instead of being scattered and reflected back out, some of the light gets absorbed. The more light absorbed, the darker the cloud appears—from pale gray to deep charcoal.
So in essence, the color of a cloud depends on how much light is being reflected versus how much is being absorbed. That’s why darker clouds often signal rain—they’re heavy with moisture and less light can pass through them.
Blue-Gray, Green, and Yellow Clouds: What Do They Mean?
- Blue-gray clouds often appear when rain is falling within the cloud and scattering light in a particular way.
- Greenish clouds may form when sunlight filters through large amounts of ice—usually in severe thunderstorms. This eerie green cast can be a warning sign of hail or even a tornado.
- Yellowish clouds tend to appear when there’s a lot of smoke or pollution in the atmosphere—like during a forest fire. The particles in the smoke alter how light is scattered and reflected.
What About Pink, Red, and Orange Clouds?
Clouds can take on stunning hues of pink, red, and orange during sunrise or sunset. But they’re not actually changing color. Instead, they’re reflecting the long, warm wavelengths of light—reds and oranges—that dominate the sky when the sun is low on the horizon. These glowing clouds create a breathtaking backdrop for the start or end of the day.
Feature and content image credit: Dr. John "Cloudman" Day. Used with permission.
