Sometimes the sky is full of white clouds. But sometimes clouds look black. Where does the colour come from?
Clouds are made of water or ice. But the drops of water in the clouds are not red or orange. The sun makes the colours in the clouds. Sunshine changes colour as it goes through the drops of water in the clouds.
Clouds look dark because they are so thick. Lots of drops of water make a cloud. Very little sunshine can go through. Dust also makes clouds dark. Dust from the ground is blown into the sky. and becomes part of the clouds.
The colours of the clouds tell about the wether.
有时天空布满了白云，可是有时云看起来是黑的。这些颜色是从哪里来的呢?
云是由水和冰组成的。可是云中的水滴并不是红色或橘黄的。太阳使云有了颜色。当阳光穿过云中的水滴是改变了颜色。
云看起来暗是因为云层太厚了。许多水滴组成了云，很少的阳光能穿透云层。尘埃也能使云变暗。地面上的尘埃被吹到空中时，它就成了云的一部分。
通过云彩的颜色能预报天气。