i don't know if this classifies as "supernatural" (the word itself actually makes it very unreal, like "super" "wow unbelievable"),
anyways :
Three years ago, i had bad dreams about cancer. Not me, or anyone i know, but just people getting cancer and dying. Several days in a row, i'd wake up after someone i don't know dying of cancer in my dreams. After several weeks, it started to feel uncomfortable. During the day i was thinking "what if ...". You know those thoughts probably. It kept going on for a month. Almost every day i saw some person dying of cancer in my dreams. I was like "hell, why not. Go see a doctor." I really went to the doctor and told him i want to have my blood taken and researched for anything that can relate to cancer. He is my long time doctor, knows me since i was a little boy. Anyways, so the research was finished a couple days after. The doctor told me no nothing in blood.
Anyways, the dreams kept going.
It came to a point i feared for something happening to my family or anyone. It took months.
So i told them about it. My elder brother was kind of "funny". Untill one night, i woke up during the night because of the same dream, but this time my sister died. (i really have tears now).
I begged my whole family, to go to the hospital and get checked. I talked to my doctor and he set up an appointment for the whole family. Eventually everyone agreed. One week later my doctor calls... Says he want to talk to my sister :(. I bursted in tears

:(
I asked him to tell me. He said he couldn't, had to talk with my sister first. Turned out she had been evolving aggressive cancer (pancreas). They started research and so on and it even turned out my father had a big aggressive polyp (which would certainly turn into cancer, according to the doc) at the same place. They immediately took it away. Surgery on sister and heavy chemo. My doctor was in awe. He asked since when i had these dreams. I said "months". He said, ok i'm a physician, but this is unexplainable. I needed to ask, i just had to, eventhough the answer could yield me an enourmous guilt-feeling. I asked how "new/old" the cancer was. He said not to worry about that, only to hope my sister gets better. I said i really want to know. He knew what i was fishing for. Took a deep breath, looked me in the eyes and literally said :
"Yes Akin, the cancer is pretty young, probably evolved from polyp to cancer during the last two months. If you could convince your family earlier to get checked, we would have probably find a polyp with your sister, instead of cancer"
So she passed away and the dreams stopped.

And i'm still thinking, two years after, "what if i told them earlier about these dreams? Why did i wait months?

godfucking damned!