Well first notice rain is not the only thing the Bible says caused the flood. "The floodgates of the watery deep were opened."
There is also the theory that only the world, as Noah knew it, suffered this calamity. Or even all of civiliation at that time was the extent of the "world" flood.
The more I learn the more I'm coinvinced it's true. So we know that a flood "could" have occurred and we have Noah saying a flood "did" occur. Is this not evidence?
So SOMETHING did happen to Noah. He described it as a flood. At what point do we stop believing his record? As soon as he mentions God?