The circumzenithal arc rings a portion of the zenith, the point overhead, and is caused by sunlight refracted through the square ends of flat ice-crystal plates in light clouds. Attached to the upper edge of the rarely-seen 46 degree halo, the circumzenithal arc is observed only when the Sun is low in the sky. While not rare, it is uncommonly seen, as most people are not in the habit of looking straight up.