Ask Don Day: What The Heck Is This Rainbow-Thing Called?

Cowboy State Daily reader Jana Erickson spotted this phenomenon in Rock Springs on Wednesday and wanted to know what it was called and how it was formed. We asked meteorologist Don Day...

Don Day

January 20, 20232 min read

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(Cowboy State Daily Staff)

When it comes to weather and things related to weather, it’s hard to stump Wyoming meteorologist Don Day.

Cowboy State Daily readers have figured that out. 

They know if they’re got on a weather question, Day can usually figure it out.

On Friday morning, Jana Erickson from Rock Springs, Wyoming sent us a photo and asked Don what the phenomenon is called.

“I first noticed what looked like a rainbow on the left side, and then realized I could see the right side also,” Erickson wrote.

She said she stopped her car and took a photo directly into the sun. “I was not expecting it to turn out,” Erickson said.

It did turn out.

“It was beautiful and made my day,” she said.

So what is it?

Day responded minutes later.

“It’s a sundog,’ Day said, explaining that it is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the sun.

“Two sun dogs often flank the sun with a 22 degree halo,” he said.

So what causes it?

Of course, Day knew that too.

“The sundog is a member of the family of halos caused by the refraction of sunlight by ice crystals in the atmosphere,” he said.

Day said they typically appear as a pair of “subtly colored patches of light” around 22 degrees to the left and right of the sun and at the same altitude and above the horizon of the sun.

They can be seen anywhere in the world, he said, but are not always as obvious or bright as the photo sent in by Erickson.

“Sundogs are best seen and most conspicuous when the sun is near the horizon,” Day added.

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Don Day