Why do you think the writer of Genesis would return to the creation of plants and climatic conditions which existed before they were created in verses 5-6?
I suppose that it is written again in the second chapter about the creation of plants to explain how climate worked. Before the Great Flood our land was watered by a mist. The fact that rain just didn’t exist in the beginning is marvellous for me.Now researchers prove that there was a special period in the history of the world when only a mist watered the earth. People who lived then didn’t know what rain is. That’s why they were troubled when Noah told them that it was going to pour with rain, they just couldn’t imagine it. So, in the 6th verse we get to know about the climatic conditions at the beginning of creation.