Art doesn’t have to be something that was created with the intention of being art. Some of the best examples of this are art in nature. While it is unlikely that inanimate objects or systems decided to express themselves the forms created can be described as art.
The patterns and lighting observed in these clouds allow anyone able to observe them to experience something equivalent to experiencing art such as a painting.The same logic that makes clouds art also applies to sunsets because people can experience sunsets like art although the sun and orbit of the earth aren’t intending to express anything.Birds singing is are and it is a form of expression. The birds are expressing themselves to other birds and although most people wouldn’t consider conversations as art most people consider songs art.