Periods and stress

Hi all. Me and my wife have been ttc for a while. She was due her period 4 days ago, it didn't come, but she is having all the usual period symptoms. Negative on the pregnancy test though. She's never missed a period before. Normally this would be a good sign but this week Hurricane Harvey hit us here in Houston and we were without power for considerable time and were trapped until it passed. Can this sort of stress make a period late? How does it work, would the period just come late or can you miss a period completely and it come next month at normal time? It would be a dream ending to a difficult week if she was pregnant but I just wanted to see if the late period could be a consequence of something else.