There are alot of possibilities. There are alot of phenomena that we've yet to explore and understand.
What some of you are describing here would be classified by believers as a type of psychic ability, the ability to see the future, whether in a dream or a vision, etc. It varies in strength from person to person. It may not hold any significant import as you cannot "predict" it. If you see an image, you don't know what it is or where it came from or what it alluded to. You can't be be sure if it's some future event or just an imagination of your mind until it happens. If you know for certain it's the future and you change it, there's no way to ever know that prior future would have actually occurred. And then you incur the consequence of the change you wrought. If you told the future and changed it to not occur or you told a future which was just imagination that didn't occur or your telling it somehow changed it, most others would view you as insane. How do you know to rely on the accuracy of it? It seems quite a dilemma.
Then you have your skeptics and logicians. They see and view the world differently and will attribute or impose their explanation and meaning unto it. The mind is a complex and intricate functioning, a grand network of which we've barely tapped into understanding. Some process which we have not yet discovered may lie at the cause of your "prophetic" vision. You think you saw some event transpired which you had dreamed of the night before when in actuality your current mindframe somehow "reshaped" itself as if that image you see now was an image of before. Or maybe there is some chemical process occuring which produces by products of delusion or hallucination, tricks of the brain.
There are those categories of people here that I've described as evident by their responses. i.e. "human memory is not trustworthy" "think of a dog...see one" "deja vu...is just mind confusion" "i have dreams like that too" etc.
Alot of theories exist, for and against these kinds of "phenomena" or "mind-chemically induced alterations". Believers will tell you that people are born with different abilities (psychic abilities) just like they are born of different dispositions and constitutions. Some are shorter, stronger, smarter, healthier (stronger immune sys), stronger bones, heal quicker, and so on, and for which some of these categories can be adjusted or changed by the attributes of the external world around the human. If you train to run, you can become faster and increase endurance. If you lift weights, you will become stronger. Your diet will vary you. Different body types have different strengths but can train in different areas to strengthen where they are weak. Big-boned, large frame people will generally be physically stronger. Small, lean people will generally be better runners. Think ectomorph, endomorph, mesomorph types. Believers of psychic phenomena believe some people are born with mind-reading (maybe the most extreme form of empathy), "natural" capability to heal others, dimensional sight (able to see different types of matter or dimensions or beings undetectable to others or scientific instruments), remote-viewing, telekinesis, and so on and so on. Scientifically, there are people who are born that can smell and taste "colors". They don't just see it, but it's also dispersed into their other senses.
The empirically-bent people, your skeptics and logicians, or nonbelievers as you may call them do not, of course, readily believe in ghosts or mind-reading or any other kind of "psychic" phenomena. There's not tangible evidence to substantiate any of these claims. There's no way to verify or test or measure these. They do not have the faculty that believers have to experience these things. If they chose to believe, it will be on faith based on reasoned assumptions; "can so many be deluded or is there something they possess that allows to believe; much like a man blind from birth who has no idea of colors yet those who can see, know colors exist." The blind man is a poor analogy but it confers what I mean by those who are born with certain faculties and those who are born with differen faculties that impact how they will view the world.