Silko's story uses the natural world to depict the life of the residents of the resevation and their uneasy relationship with the whites who have forced them to live on the margins. 

The symbolism of the weather helps Silko make her point.  The heat of the day is contrasted with the cool snow Ken observes atop the mountain range:

He squinted up at the sun and unzipped his jacket. It sure was hot for this time of year. But high and northwest the blue mountains were still deep in snow.

In Native American mythology, the sun represents the highest form of worship of the Great Spirit.  Ken's looking to the sun, then, may represent his longing for a return to the old ways, while the snow and cold on the mountains might be an indication that such a hope is a long way from reality. 

The symbolism of shadows works its way into the story in a subtle way:

The priest turned away from Leon and looked out the window at the patio full of shadows and the dining-room windows of the nuns' cloister across the patio. The curtains were heavy, and the light from within faintly penetrated; it was impossible to see the nuns inside eating supper.

Shadows, in Indian spiritual beliefs, indicate the presence of the Trickster, that evil being who leads the People into trouble.  It's not hard to see that the priest and the nuns are representative of the Trickster.