Weather, including rain, happens as a result of natural and teleological processes, but that is compatible with the claim that rain falls not for the sake of something, but of necessity, and any benefit from the rain comes by chance. Aristotle need not embrace the conclusion, therefore, that it rains for the sake of the crops. Climate, on the other hand, is regular and beneficial. If the disjunct from Physics II.8 holds, climate ought to be for the sake of something even while rain is not.
Dominick, Yancy Hughes, "Climate and Teleology in Aristotle's Physics II.8" (2011). The Society for Ancient Greek Philosophy Newsletter. 394.