The Bible says it never rained before the flood and it’s obvious from the language of Genesis that survivors viewed the rainbow as seriously strange and new.
Right, exactly, so I think a tidal pull isn’t exactly the answer, since water would have just rushed in rather than a build up through the rain from the heavens, or maybe a tidal pull would act weirdly (”slap around” like a rubberband after being released?). Just thinking.
It simply didn't state that it didn't rain.