The sun is an omnipresent force in the Joads' life, one that they cannot escape. Many Joads have to sit on top of the family truck on their way to California, and our narrator describes, "Their faces were shining with sunburn they could not escape" (13.18). In this way the sun is almost violent. We also know that there has been a devastating drought in America over the past decade, which has contributed to the arrival of Dust Bowl storms. The sun is a dangerous power.
However, the sun is not always a destructive symbol in this novel. Our narrator describes the sun in hopeful language when he says, "The red sun set and left a shining twilight on the land, so that faces were bright in the evening and eyes shone in reflection of the sky. The evening picked up light where it could" (13.174).