How does the setting in the first two paragraphs foreshadow what happens?
With the description in the first two paragraphs of the dormant Salinas Valley that in the winter is a "closed pot," there is the suggestion of what is to come. "The grey-flannel fog of winter" shuts the valley off from its surroundings much as Elisa's passionate nature lies dormant as it, too, awaits the sunshine of human interaction.
On a ranch with no other women, Elisa Allen finds little outlet for her creative drive and energy except for her work in the flower garden in which she zealously cuts the old chrysanthemum stalks and digs with "her terrier fingers" in the ground to remove any pests that might attack her flowers. Much like the fog described in the opening paragraph, "a cloud of hair" hangs in her eyes.
When the tinker pulls up with his wagon and Elisa talks with him, she becomes hopeful of sharing some human emotion with this vibrant man. And, because Elisa tells him she has no work for him, he lingers in the chance that there may yet be something for him; then, noticing how she attends her chrysanthemums, he asks her about them under the pretext of obtaining some seedlings for another woman. Eagerly and passionately, Elisa responds with much the same manner as the farmers in the second paragraph are "hopeful of a good rain."
But, "rain and fog do not go together." Elisa's passion is not matched by the tinker, nor is it stirred enough in her husband as they head to town for an evening out. Certainly, her excitement for their evening is diminished when she finds the flower which she has given the tinker thrown out onto the road, causing her to cry.