Genesis says the floodwaters prevailed over the Earth for 150 days.
Genesis 7:24 gives this figure after describing the waters rising over the land. The number is distinct from the forty days and forty nights of rain mentioned earlier. Genesis later says God remembered Noah, caused a wind to pass over the Earth, and made the waters begin to subside.
The flood story contains several overlapping time references, which can make the chronology easy to mix up. The rain lasts forty days and nights, the waters prevail for 150 days, and the complete sequence from Noah's entry into the ark to his departure is presented as lasting roughly a year in the text's calendar framework. Different translations and chronology calculations can emphasize slightly different details.