Question: why do clouds change shape, like really puffy or really thin and spread out?

Chris Armstrong answered on 18 Jun 2015:

Clouds are actually really complicated, I don’t understand anything bar the basics of formation. There are loads of different types of clouds that form through various process. The really puffy are Cumulonimbus and are huuuge rain bearing clouds that generally span from the very bottom of the cloud level up to like 40000ft, the wispy thin ones are called stratus clouds and only really form on the lower levels.

The big ones form slowly from water vapour being drawn up through them by hot currents, whereas the whispy ones form from large uplifts of moisture from the ground.

In a less specific case, the shape is dependent on how the cloud develops, the air currents around the cloud and moisture available.