In the story as a whole, how do setting and plot reinforce each other?

The setting reinforces the plot. The chance that Calixta would have dallied with Alcee had not the storm delayed her husband and son..... or if someone had been in or around the house are nil and none. The storm insured the two would be alone (really alone), and it also set the stage for rekindling an old flame between them. Once the storm was over, they both went back to reality.