In the Genesis flood narrative, the floodwaters prevailed for 150 days.
Genesis presents the flood as a sequence rather than a single event of one length. Rain fell for forty days and forty nights, but the waters continued to rise and remain powerful afterward. Genesis 7:24 states that the waters prevailed on the earth for 150 days.
The figure is therefore different from the familiar forty-day rainfall. After this period, Genesis says that God caused a wind to pass over the earth, and the waters began to subside. The ark later rested, and Noah eventually sent out birds to test whether the land had reappeared.
Chronological readings of the narrative can be complex because the text gives several overlapping time markers. The 150-day figure is nevertheless one of its clearest stated durations. It belongs specifically to the Genesis account and should not automatically be applied to other flood traditions.