The following information is from "Google" and helps explain the phenomenon.

Sundogs can be seen worldwide and can appear at any time when the sun is above the horizon. There are, however, conditions that not only make sundogs more likely to manifest but also boost their brightness making them more likely to be seen.

The most obvious condition improving the quality of sundogs is the proximity of the sun to the horizon. The closer the sun is to the horizon the more conspicuous sundogs are. When the sun is high in the sky sunlight can't pass through ice crystals as easily.

Because sundogs are more common when the sun is close to the horizon, the best time to look for these solar illusions is in the morning or evening when the sun is rising or setting.

The fact that ice is key to the creation of sundogs means you are more likely to see them during winter, especially the further north you go.

A sundog is a concentrated patch of sunlight that is occasionally seen to the right or the left of the sun or even on both sides of our star in the sky simultaneously.

Joe Svoboda captured the US flag within the Sun-Dogs.

Also called mock suns or perihelia, meaning "with the sun," according to the National Weather Service. Sundogs are part of a family of atmospheric optical illusions including moon haloes and the closely related sun haloes. All of these phenomena are caused by the refraction of sunlight by ice crystals in the atmosphere. 

Sundogs typically appear as a pair of patches of light with subtle colors which manifest at the same altitude over the horizon as the sun. They can appear in a variety of forms, sometimes as colorful spots, or other times, so intense and bright they appear to be two additional suns in the sky.