Why is the sky sometimes yellow and black?

Yellow usually appears in spring, and sandstorms are rampant. The yellow sand particles blown from the northwest desert will be blown to most parts of the country with the strong northwest wind. In addition, yellow is extreme weather. People say it's black wind and yellow rain. Generally, in summer, the weather changes quickly. Sometimes when filling in the blanks, dark clouds will cover the sky in a short time, sometimes it is a gust of wind, and when it is yellow, it is often a rainstorm.