Did anyone see this phenomenon over the weekend? NASA says this sun halo is formed when sunlight shines through ice crystals in the air.
EarthSky.org: There’s an old weather saying: ring around the moon means rain soon. There’s truth to this saying, because high cirrus clouds often come before a storm. Halos are a sign of high thin cirrus clouds drifting 20,000 feet or more above our heads.
These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear.
This photo was taken outside of the Seattle Southside Visitor Center. That's our flag in the center of the halo!