彤云密布

Explanation: Clouds: Tong is the meaning of red, sometimes referred to as Hongxia; sometimes referred to as a cloud of snow before the uniform clouds. Very thick clouds covered the sky, indicating that snow is coming. 　　Source: "Book of Songs Xiaoya Nanshan letter," God with clouds, rain and snow atmosphere atmosphere. " 　　Examples: ~, Cold fog colorful. (Ming Xu Zhonglin "Gods" eighty-ninth back) Thesaurus:  rain cats and dogs