What Are Sun Dogs? Rainbows Beside the Sun!

What Are Sun Dogs?

The short answer: A sun dog, or parhelion, is a bright patch of light—often rainbow-colored—that appears beside the Sun when sunlight refracts through ice crystals in high clouds.

A sun dog is similar to a rainbow and is more common. 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.

Sun dogs 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 sun dogs.

Both rainbows and sun dogs are formed by moisture filtering the sunlight.

Rainbows form when drops of rain act as prisms, breaking sunlight into a multitude of colors. Sun dogs 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 sun dog is seen about 22° to the left or right of the Sun. Sun dogs 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 sun dog. 

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 sun dogs, sunlight is refracted through ice crystals; these hexagonal ice crystals are suspended in cirrostratus clouds. 

Viewing a Sun Dog

There are some differences between rainbows and sun dogs, however.

• You see rainbows when you look away from the Sun.
• You see sun dogs 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 sun dogs when the Sun rises or sets near the horizon. (Sun halos can appear anywhere, even when the Sun is high in the sky.)

Frequently Asked Questions

What Does It Mean When You See a Sun Dog?

A sun dog often means that rain is on the way—often within the next 24 hours. Next time you see a sun dog, look out for foul or wet weather!

Are Sun Dogs Good Luck? 

In medieval times, the three bright lights were sometimes interpreted as a sign of the Trinity, a sign of great fortune. Nowadays, seeing a rainbow or a sun dog 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.

What causes a sun dog?


Sun dogs form when sunlight is refracted through hexagonal ice crystals in cirrus or cirrostratus clouds. The light bends at a 22° angle, creating colorful patches beside the Sun.

When can you see a sun dog?


You’re most likely to spot sun dogs when the Sun is low on the horizon—around sunrise or sunset—especially on cold days with thin, icy clouds overhead.

What’s the difference between a sun dog and a sun halo?


A sun halo is a full circle of light around the Sun, while sun dogs appear as two bright spots to the left and right of the Sun. Both occur when sunlight refracts through ice crystals.

Can you see sun dogs at night?


Yes! When the same effect happens with moonlight instead of sunlight, it’s called a Moon dog or paraselene.

Learn more about how rainbows form.

Have you ever seen a sun dog or sun halo? Share your sky sighting with us in the comments!