Allegorical maybe?

I like the interpretation of this movie as being an exploration of mental illness and the effects on the individual and his family, but maybe the whole movie is allegorical. Perhaps, the movie is about the ongoing debate about global warming/climate change and the possible cataclysmic events that would result. In this allegory, Curtis would be those of us that believe that global warming is a reality we all face, and that its environmental impact is imminent. Those that think he's losing his mind, are those that deny these beliefs and dismiss these warnings as paranoid delusions or fear-mongering.

One of the reasons I thought that this may be an allegory, is the rain that he dreams about at the beginning and which reoccurs at the very end. It seems the result of heavy pollution and the environment reaching a breaking point. Also, the storm seems like a massive tsunami caused by the disruption of balance within our ecosystem which is reminiscent of predictions of the types of storms we will see more and more often as the effects of climate change become more prevalent.

Of course, then, if the movie is allegorical, the ending involves both sides realizing this is an undeniable reality that we have to face and address together, in hopes that a solution can still be achieved.