The floodwaters prevailed over the earth for 150 days in Genesis.
Genesis 7:24 states that the waters prevailed upon the earth for 150 days. This figure is distinct from the forty days and forty nights of rain mentioned earlier in the same chapter. The rainfall period describes the storm, while the 150-day figure describes how long the floodwaters remained dominant.
Genesis 8 then describes the waters gradually abating. The ark comes to rest on the mountains of Ararat, the mountain tops become visible, and Noah uses the raven and dove to test whether the ground is dry. The narrative eventually ends with Noah leaving the ark after receiving God's instruction.
Readers sometimes combine all the numbers in the story into one total, but they mark different stages. Genesis also gives several dates in Noah's six-hundredth year, showing that the complete episode lasts far longer than either the rain or the 150-day period alone.