All About Sundogs - Rainbows beside the Sun! | The Old Farmer's Almanac

What Are Sundogs? Rainbows Beside the Sun!

sun dog, a atmospheric phenomenon, also called parhelion
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What Are Sundogs? And How Did They Get Their Name?

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Have you ever seen a rainbow-colored patch of light on the side of the Sun? This is called a “sundog.” Why are they called sundogs? How do you view one? And what do they mean weatherwise? Find out!

What Are Sundogs?

A sundog is similar to a rainbow and more common than rainbows. Sometimes, they look like bright rainbows or colorful spots on either side of the Sun. Other times, they are brighter and actually look like two extra Suns.

Sundogs are also known as “mock suns” or “parhelia,” which means “with the Sun.” The most common name, however, for these bright lights that faithfully follow the Sun is “sundogs.”


Both rainbows and sundogs are formed by moisture filtering the sunlight.

Rainbows form when drops of rain act as prisms, breaking sunlight into a multitude of colors. Sundogs appear when sunlight passes through a thin veil of ice crystal clouds (usually cirrus or cirrostratus), and the ice acts as a prism, refracting the light. 

A sundog is seen about 22° to the left or right of the Sun. Sundogs often form in pairs on either side of the Sun. Often, they appear white, but sometimes they are quite colorful, looking like patches of rainbow. The colors usually go from red on the side nearest to the Sun, shifting from orange to blue on the outside of the sundog. 

Like rainbows, sundogs are created when sunlight is filtered by moisture in the sky. Used by permission HyperPhysics, C.R. Nave Georgia State University.

What are Sun Halos?

You may have heard of a related phenomenon called a “sun halo.” In this case, it’s an entire circle of light  22° wide around the Sun. Like sundogs, sunlight is refracted through ice crystals; these hexagonal ice crystals are suspended in cirrostratus clouds. 

Viewing a Sundog

There are some differences between rainbows and sundogs, however.

  • You see rainbows when you look away from the Sun.
  • You see sundogs when you look toward the Sun. If the ice crystals fall flat, you see a bright light point on either side of the Sun. 

Look for sundogs when the Sun rises or sets near the horizon.  (Sun halos can appear anywhere, even when the Sun is high in the sky.)

What Does It Mean When You See a Sundog?

Probably the most significant difference between the two is that a rainbow usually signals an end to the rain, while a sundog often means that rain is on the way—often within the next 24 hours. Next time you see a sundog, look out for foul or wet weather!

Are Sundogs Good Luck? In medieval times, the three bright lights were sometimes interpreted as the sign of the trinity, a sign of great fortune. Nowadays, seeing a rainbow or a sundog is a sign of good luck (or, perhaps, just being at the right place at the right time?). 

How Did the Name “Sun Dogs” Come About?

According to Greek mythology, Zeus walked his dogs across the sky, and those  “false suns” in the sky on either side of the sun’s disk were his two dogs.

Now you get to see those faithful companions of our sun—the sundogs!  We can also see Moon dogs!

Learn more about how rainbows form.

About The Author

James J. Garriss

With an academic background in international business, James is a writer, editor and researcher for Browning Media LLC, helping to present accurate climatological projections. Read More from James J. Garriss