What is the central meaning of the first paragraph in weather selection? What is the function of this paragraph in the full text?

The central meaning of the first paragraph of weather selection is that the clouds in the sky are really changeable. This paragraph has the function of highlighting the central idea of the full text.

The first paragraph of the original text

The clouds in the sky are really varied and changeable. Some are like feathers, floating gently in the air; Some are like fish scales, neatly arranged one by one; Some come and go like sheep; Some are like a big quilt, covering the sky tightly; Others are like mountains, rivers, lions and galloping horses ... sometimes they decorate the sky beautifully, and sometimes they cast a shadow over it. Just now, it was white clouds and the sun was shining; In a blink of an eye, it was cloudy and it rained cats and dogs. Clouds are like the "signboard" of weather: what kind of weather will appear when there are clouds hanging in the sky.