Residents of the city of Puning, south China’s Guangdong province, photographed and videotaped a rainbow scarf cloud enveloping a growing rain cloud. Such clouds are also called pileus (pileus): they received this name for their resemblance to the ancient Roman hat. Sometimes even several clouds are observed strung one on top of the other. This time there was only one pileus, but it was rainbow-coloured. The rainbow cloud was formed as a result of cooling and condensation of moist air, in which solid ice particles were present. Sunlight, directed at a right angle, is refracted between drops and ice crystals…