The circumhorizontal arc, or the fire rainbow, is an optical phenomenon caused by the refraction of sunlight through thick, flat, horizontal ice crystals in cirrus clouds. Atmospheric conditions have to be very specific and perfect, and it can only be observed in certain locations of the world.
To get an idea of just how truly complicated things have to be for it to form, check out this quote from Wikipedia: “In order to be observed, the sun must be very high in the sky, at an elevation of 57.8° (90 -32.2°) or more, and can only occur in the presence of cirrus clouds. As a result it cannot be observed at locations north of 55°N or south of 55°S, although occasionally at higher latitudes from mountains. In areas of Northern Europe it can only be observed around the time of the Summer solstice. If cloud conditions are right it is seen along the horizon on the same side of the sky as the sun. It reaches its maximum intensity at a sun elevation of 67.9°