What is the irony in "The Storm" by Kate Chopin?

The irony in this excellent short story lies in the impact
of the adulterous relationship between Calixta and Alcee on their marriages. There is
situational irony in the way that we expect that such a tempestuous (no pun intended)
session of lovemaking, which is presented very explicitly but also in a way that
suggests that Calixta and Alcee are somehow meant for each other actually benefits their
respective marriages. Note how their union is
presented:

Her
firm, elastic flesh that was knowing for the first time its birthright, was like a
creamy lily that the sun invites to contribute its breath and perfume to the undying
life of the world.

Phrases
such as Calixta knowing her "birthright" whilst having extra-marital sex with Alcee
suggest that she will be unable to return to her husband after this. However, after the
storm of passion that has been unleashed, the air appears to have been cleared, and both
Calixta and Alcee are shown to return even happier than before to their respective
partners:

So
the storm passed and everyone was
happy.

This is the irony in
this excellent short story, as Chopin shockingly suggests that such outlets of
tempestuous passion can actually help marriage rather than destroy
it.