In the biblical Flood story, the waters prevailed over the earth for 150 days.
Genesis 7:24 states that the waters prevailed upon the earth for 150 days. Genesis 8 then says that God remembered Noah and caused a wind to pass over the earth, after which the waters began to subside. The 150-day figure is therefore part of the Flood chronology after the rising waters had covered the land.
This number is often confused with the 40 days and 40 nights of rain. The two figures describe different parts of the narrative: rain falls for 40 days and nights, while the waters continue to prevail for 150 days. The text also gives dates in Noah’s life to mark the Ark’s resting and the later drying of the ground.
Some readers notice apparent chronological tensions among the Flood passages, especially when comparing different time markers. Nevertheless, 150 days is the explicit duration given in Genesis 7:24 for the waters prevailing.