What is a sun dog and why is it so beautiful this morning?

As the region began its plummet into a once-in-a-generational cold snap, the sun provided a unique silver lining. 

Two large bright spots flanked the sun in Sioux Falls and across the region on Tuesday morning. The atmospheric phenomenon is called sun dogs. 

Andrew Kalin with the National Weather Service said that the atmospheric phenomenon appears when sunlight refracts off of ice crystals in the atmosphere — and at temperatures like those we have today, there are plenty of ice crystals.

They're more noticeable when the sun is closer to the horizon, as the atmosphere is thicker close to the ground.

Temperatures reached minus-9 Tuesday morning and were expected to reach minus-28 on Wednesday. With the wind chill, it will feel like minus-50 or lower.