When I parked at Lowe’s this morning I looked up towards the sun and saw this.

Solar halo, possibly a parhelic halo — click to enlarge

This was taken at about 11:30, so the sun was nearly at its highest point. Since it’s just at the start of winter, the sun’s highest point is pretty low in the sky. I stood so the sun was directly behind the parking lot light fixture. There was an almost complete halo around the sun. I think it was at the same angular distance from the sun as a sundog or pahelion, but since the sun is so high there was no really bright point at the sun’s elevation above the horizon. You can see that the sky is darker inside the halo, because the ice crystals don’t reflect/refract very well into angles smaller than where the halo appears. This halo was probably caused by columnar ice crystals, which orient randomly. That allows the halo to form all the way around the sun. The clouds were coming in advance of a cold front. They were just the right thickness to make the halo visible. When I came back out about 15 minutes later, the halo was no longer visible. Of course the ice crystals were still there in the clouds, and they were refracting the same way, but the thickness of the clouds had increased so I couldn’t see it on the ground.