A halo of light hung above the mid-summer sky of Pingtan, E China's Fujian province, on July 19. The luminous ring encircling the sun drew a flurry of onlookers and drove social media abuzz. This spectacular optical phenomenon is called a sun halo which occurs when sunlight reflects through millions of ice crystals trapped in cirrostratus clouds. Its appearance is a good omen amid the scorching summer heat. As the saying goes, "A sun halo brings midnight rainfall."