Apparently fire rainbows (fancy name circumhorizontal arc or lower symmetric 46 degree plate arc) are rarely seen, which is a pity because this natural phenomenon is incredibly beautiful, almost ethereal.
Two main things have to happen for a fire rainbow to occur. The sun has to reach at least 58 degrees in the sky and cirrus clouds have to be present. In addition, fire rainbows only occur between 55 degrees N and 55 degrees S, so if you live above or below those latitudes you would have to travel to see one.
Cirrus clouds are fine, feathery clouds that occur at high altitudes where it is very cold. So cold that these clouds are actually made of ice crystals. These ice crystals act as prisms and when sunlight shines through them the light is refracted (or bent) and rainbows are formed in the clouds.
This afternoon the sun reached the perfect height, there were plenty of clouds and I was in just the right place to witness one of Nature’s miracles.
As a bonus I’m including this remarkable photo that Piet took on New Years Eve a few years ago.