I saw this ring around the sun while backpacking Colca Canyon near Arequipa, Peru. What causes this halo? Rings around the sun are formed from the refraction of sunlight through tiny ice crystals high in the sky, similar to how a rainbow is formed. These clouds of ice crystals are called cirrus clouds. The halos, called 22-degree halos, typically form at a 22-degree radius from the sun. These rings often precede a warm front and can mean that rain is on its way, although there was no rain at the canyon that day, or the next, or the next. Similar halos can also be seen around the moon.
