According to a piece published in The Conversation researchers have drawn links between brain activity and déjà vu.
One theory suggests that déjà vu may be caused by a similar reaction as seizures.
Beginning in the medial temporal, seizures are an electrical overload in the brain. Scientists believe that this could explain why you think you've seen it all before. Reporters believe that if an electrical overload occurs in the rhinal cortices portion of the brain, a false signal would be sent, convincing the brain that it's seen something before that it hasn't.
However, that wasn't the only possible reason for the experience.
Investigators believe that déjà vu could also be caused by memory failure. At times, if the brain is unable to categorise an event in the short-term memory section of the brain, instead it files it away in the long-term memory section. Your brain tricks you into thinking that you've experienced this situation before.
You may also note the sudden confusion you experience after your own ground hog day experience. Science believes that's caused by your brain trying to correct itself.
While scientific theories pose the most reasonable explanations, of course there are plenty of guesses that you might only expect to see in a Sci-Fi thriller.