Iridescent clouds have rainbow colors

Iridescent clouds: Colorful clouds above a tree-and-snow-covered ridgeline — View at EarthSky Community Photos. | Wendy Rae captured this image in late January 2022 and wrote: “Here in the Elkhorn Range in Montana, we are treated to cloud iridescence fairly regularly, both solar and lunar. This was the best display I’ve seen and was immediately visible once the sun dipped behind the mountain.” Thank you, Wendy!

Clouds with rainbow colors

Sky watchers often report seeing rainbow colors in clouds. There are many different kinds of rainbow features you might see associated with clouds, such as halos and colored arcs and even true rainbows. But – if the rainbow-like colors are randomly distributed, and if the sun is nearby in the sky – what you’re seeing is likely an iridescent cloud.

These sorts of clouds are caused by particularly tiny ice crystals or water droplets in the air. Larger ice crystals produce lunar or solar halos, but tiny ice crystals or water droplets cause light to be diffracted – spread out – creating this rainbow-like effect in the clouds.

The images on this page are mostly via the EarthSky community. Our thanks to all who contributed!

By the way, it’s easy to confuse circumhorizon arcs with iridescent clouds. Here’s how to tell the difference.

A gallery of images of iridescent clouds

Sky full of clouds with green, orange, yellow, pink, purple and blue colors. — View at EarthSky Community Photos. | Shreya Roy in Kolkata, West Bengal, India, captured this beautiful display of iridescent clouds before sunset on July 19, 2023. She wrote: “These sorts of clouds are caused by particularly tiny ice crystals or water droplets in the air. Tiny ice crystals or water droplets cause light to be diffracted – spread out – creating this rainbow-like effect in the clouds.” We couldn’t have put it better, Shreya! Thank you.

Dark cloud with cap of rainbow colors on dark sky. — View at EarthSky Community Photos. | Soumyadeep Mukherjee in Kolkata, West Bengal, India, captured this photo of iridescent clouds on August 5, 2021, and wrote: “Iridescent clouds, also known as rainbow clouds, are an optical phenomenon caused by diffraction of sun/moonlight on water droplets or small ice crystals on clouds. This image was captured before sunset. As I woke up after a noon nap and looked through the window, I was greeted by this beautiful cloud and I had to run. I took the wrong lens and the whole thing wouldn’t fit on the frame. Hence, a two-shot handheld panorama. I’m glad that it came out decent.” Thank you, Soumyadeep!

More iridescent clouds

Reddish sky, bright star, and a full moon in the middle of a cloud with colors. — The moon with Jupiter and iridescent clouds, seen over Greece in 2015 by Nikolaus Pantazis.

Dark blue sky with clouds at bottom and rainbow clouds in the middle. — The colors in an iridescent cloud tend to be subtle and are usually pastel, but in some cases they can be vivid. Here is cloud iridescence captured by George Quiroga in Boynton Beach, Florida, in 2012. Image via Wikimedia Commons.

Bottom line: You might someday see an iridescent cloud. These clouds have rainbow-like colors. They’re caused by very tiny ice crystals or water droplets in the air, which cause light to be diffracted (spread out).

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