(National Weather Service)

Turns out, there’s a sunny side to the arctic conditions Chicagoans have been experiencing in recent days.

Not only has the sun been visible, it’s been putting on a show thanks to ice crystals in the air, creating “sundogs.” For those who aren’t familiar with the term, it looks a bit like rainbow-esque parentheses, with the sun in the middle, or can even resemble a second sun.

Sundogs — known technically as parhelia or more casually as “mock suns” — form when waves of sunlight pass through ice crystals suspended in clouds. The crystals refract, or bend, the light 22 degrees to the sun’s left, right or both, resulting in an arc or even halo, according to the National Weather Service.

The Chicago office of the National Weather Service shared a photo of this well-known phenomenon, taken Sunday, and people from around the region, including other scientists, chimed in with images of their own. 

Cold weather means sun dogs!! #ilwx pic.twitter.com/scwRbPxYl4

— Scott Collis (He/Him) (@Cyclogenesis_au) January 16, 2024

The name sundog purportedly originates with Greek mythology and refers to the god Zeus walking his dogs across the sky — the mock suns are the dogs.

Sundogs can be seen around the world, but certain conditions lead to more brilliant displays.

The closer the sun is to the horizon, the better the view, according to experts, and that means sunrise or sunset. The presence of ice crystals is a necessary ingredient, making winter the ideal time to spot a sundog.

Take a look at these images of spectacular sundogs, captured everywhere from Scandinavia to Minnesota.
(U.S. Fish and Wildlife Service Midwest Region / Flickr Creative Commons)
(Alan Levine / Flickr Creative Commons)
(Yellowstone National Park / Flickr Creative Commons)

Contact Patty Wetli: @pattywetli | (773) 509-5623 |  [email protected]