I can't believe I have to explain this.
Some stories aren't stories at all. They're genetic memories. Life on this Earth began from a very hot, very steam place. People like to talk about meteors but no there was life, it just got a jumpstart. The life we are speaking about are bacteria of a sort suited to hostile life. If you had (like most humans do) genetic code from previous beings, you'd have information as a sort of garbled racial memory of all the Earth being land (speaking frankly, a hot land). Then suddenly, moisture collects, and it collects, and it collects, until the world is flooded. This isn't a rainstorm btw. This is a Paleozoic flood period where most of the life is marine. And then suddenly it isn't, you're a genetic group that became suited for dry land. In fact, this happens a few times. Remember the test where they sent out birds? These are false dry periods, where there is some land but the land doesn't really come back.
In other words, no we're not describing a rainstorm. Millions of years of evolution is having a brain fart, and telling a story they shouldn't be able to know.
Or it could be the Black Sea inundation. But a flood def happened.