The excerpt from 'The Man to Send Rain Clouds' containing a simile compares the water's fall to August rain.
The excerpt from Leslie Marmon Silko's story "The Man to Send Rain Clouds" that contains a simile is:
the water fell through the light from sundown like August rain that fell while the sun was still shining.
A simile is a figure of speech that compares two different things using the words "like" or "as," in this case, comparing the water falling through the light to August rain falling while the sun is still shining.