Cirrus clouds are beautiful things, forming all kinds of fantastical wispy shapes. They also cause quite an array of gorgeous optical phenomena: Sun dogs, which are bright coloured patches just over 22º away from the sun; circumzenith arcs, beautiful dry-weather rainbows high up in the sky; and halos at 22 and 46 degrees away from the sun, which are particularly associated with cirrostratus. Sun dogs and circumzenith arcs, on the other hand, are mainly found in thicker cirrus formations consisting of horizontally-aligned plate-like ice crystals.