The narrator's tone in this story is one of enabling encouragement. The voice we hear seems almost to be encouraging the characters in their decisions to have affairs and keep them secret, or to even bring people together through the almost magical power of the cyclone that's raging around them.
The tone seems to sympathize with the fact that Alcée and Calixta's affair can only last as long as the storm itself: that when it ends they must part rather than falling asleep together. When each character enters the story to speak or share his or her ideas, the tone melds around that person and provides sympathy for that point of view. Bibi's concern, Bobinôt's worry, Calixta's desire, Alcée's graceful deceit, and Clarisse's relief are all conveyed with equal measure. The tone presents them all as equally valid ways of approaching the world.