Ending... Explained
Just a quick prenote. I was thinking that when he opened the shelter doors after the storm passed everything was gonna be knocked down by Katrina lol and he would be relieved that he was not as crazy as he thought.
Anyways, you have to look at the scenes of events. They all lead up to the ending, and it wouldn't make sense if the storm was real, defeats the whole purpose of the movie actually. It's a slow progression of a man becoming schizophrenic, and no matter how hard he wants to be normal or be fixed, its inevitable, the illness wins.
I'll start with the scene where he yells at everyone at the Lions Club potluck saying that the storm is coming, is the scene where the audience can conclude that this man has gone crazy.
The next scene we wake up to the storm and how they rush in there. He makes them put the gas masks on regardless of whats going on outside (which he didn't understand himself what he bought them for, just schizophrenia). Next they woke him up and tried convincing him to open the door. Half of him knew the storm was over but the schizophrenia made him so scared to open it. The wife knew that this was a big step in helping his illness. If she opened the door the schizophrenia won and he would still be scared. However, if he opened the door he knows that the side that knew there wasn't a storm anymore was right all along and he would feel more normal.
The next scene was in the psychiatrists office. The scene ended with him feeling gloom about spending time apart with his family, but the wife reached in and grabbed his hand.
It cuts scenes and goes to the beach. Instead of only him seeing the storm, the whole family does. The whole family is hear to help battle his schizophrenia, which is why the wife grabbed his hand.
Lastly, If the attentions were to have the storm be real they would of done that when he opened the shelter doors and they wouldnt of wasted time and filmed the psychiatrists office scene. Plus this is why the scene where he opens the doors was so intense. Besides the tear between his own will power and the schizophrenia, there was a small thought in the back of the audiences mind saying "What if that storm was real."