How we cite our quotes: (Section.Paragraph)
Quote #4
He expressed an intention to remain outside, but it was soon apparent that he might as well have been out in the open: the water beat in upon the boards in driving sheets, and he went inside, closing the door after him. (2.4)
Social propriety is no match for the natural world here. Alcée would normally stay outside the house, so he and Calixta aren't alone together in her domestic space. But the weather has other plans: with "the water beat[ing] in upon the boards in driving sheets," there's no way he could stay outside. Conveniently, he has to come in to wait out the storm.
Quote #5
The rain beat upon the low, shingled roof with a force and clatter that threatened to break an entrance and deluge them there. (2.8)
The storm is practically personified here, "threaten[ing] to break" in on Alcée and Calixta and "deluge them" in Calixta's own house. Just as the rain didn't respect Alcée's commitment to social propriety, it threatens to follow him into the house where it's not wanted.
Quote #6
She went and stood at the window with a greatly disturbed look on her face. She wiped the frame that was clouded with moisture. It was stiflingly hot. Alcée got up and joined her at the window, looking over her shoulder. The rain was coming down in sheets obscuring the view of far-off cabins and enveloping the distant wood in a gray mist. The playing of the lightning was incessant. A bolt struck a tall chinaberry tree at the edge of the field. It filled all visible space with a blinding glare and the crash seemed to invade the very boards they stood upon. (2.14)
Just in case we didn't realize how hardcore the storm is, here's a reminder. The heat is "stifling." The sky is full of "rain," "mist," and "lightning." The lightning is close, too, since it hits a "tree at the edge of the field" near Calixta's house. This should eliminate any doubt that the characters are overreacting to the storm or that their fear isn't justified.