Though called fire rainbows, they are neither fire nor rainbows. Actually, fire rainbows form in clouds and are called so due to their colors and their appearance, similar to flames. Scientifically, they are known as circumhorizontal arc and are basically an ice halo formed by hexagonal, plate-shaped ice crystals. Fire rainbows form in Cirrus clouds and are so large that they appear to be parallel to the horizon. Though impressive, fire rainbows are rare and cannot be seen from everywhere, which is quite a pity as they are so beautiful and fascinating.
Fire rainbows occur mostly in summertime, but only between certain latitudes. The conditions under which they occur are very strict and precise: the sun has to be very high in the sky, and its light must enter flatly, causing the hexagonal ice crystals to split into individual colors. The sun has to be at an elevation of at least 58°, there have to be high level Cirrus clouds, the light has to enter the crystal at a precise angle. As you have probably deduced by now, due to all this precise requirements, fire rainbows are a rare phenomenon.
Of course, whether you will actually see a fire rainbow depends on where in the world you live. They cannot be seen in locations north of 55°N or south of 55°S. Also, fire rainbows are not the same with Iridescent clouds, though they appear similar. Iridescent clouds occur rarely in Cirrus clouds and mostly in other types, such as altocumulus or cirrocumulus.
Fire rainbows are impressive indeed, as they are so rare and so beautiful. Maybe it is because they require such precise conditions that they are so fascinating. What do you think?Have you ever seen one? We would love to read your thoughts and impressions on this phenomenon in the comment section below.
All photos come from amusingplanet.com