Drawing the sky with a pencil is not easy. 3D shapes of clouds are difficult to depict using conventional hatching.
However, if you follow a certain algorithm, you can get a good, rather realistic result.
Draw a few basic outlines. Remember that the clouds are very rarely round. In addition, it all depends on the type. The size of the clouds may also vary. If you want to depict something truly beautiful, take one big cloud and many small ones.
Add loops to the contours. Some of the small clouds make it pinnate. That is, the wind should literally carry them along the horizontal plane. The others give a little volume by increasing the rounded parts.
Circle the outlines of clouds with a thicker line. Mark the specific areas of hatching and further detail the picture.
Add the earth under the sky. This will make the drawing more realistic. Hatch light and dark sides with hatching, adding volume. Note that the clouds are very far away, so the shadows should not have clear outlines.