In the Genesis account, Noah waited forty days after the mountaintops appeared before opening Noah’s Ark.
Genesis 8:5 says that the waters continued to decrease until the tops of the mountains became visible. Verse 6 then says that after forty days Noah opened the window of the ark and sent out a raven. This is a separate forty-day interval from the earlier forty days and nights of rain.
That distinction creates several numbers in the flood chronology. Rain falls for forty days and nights, the waters prevail for 150 days, the mountaintops appear, and Noah then waits another forty days before opening the window.
Readers sometimes combine these intervals into one figure, but the sequence in Genesis treats them as different stages. The text’s repeated numbers are part of its narrative structure and should not be collapsed into the duration of the entire flood.