The SA Weather Service, confirming the pictures show an iridescent cloud, said on Wednesday iridescent clouds are quite often encountered at higher latitudes.
Chief forecaster Kevin Rae said iridescent clouds occur when rays of sunlight shine through a thin layer of cloud comprising ice crystals.
“Such clouds are, in meteorological terms, referred to as cirrus or cirrostratus clouds. The public would be very familiar with the common phenomenon of rainbows, when falling rain, drizzle or sometimes fog is ‘backlit’ by bright sunshine. The rainy region acts as a giant prism, splitting up the light into its component colours according to (longer/shorter) wavelengths,” he said.
Rae said in the case of an iridescent cloud, the process is exactly the same, only a thin layer of ice crystals is substituted to act as the prism.
“The result is that particular section of cloud will appear to shine or glow in rainbow colours,” Rae said.