In Genesis’s Noah’s Ark account, the floodwaters prevailed on the earth for 150 days.
Genesis 7:24 says the waters prevailed upon the earth for 150 days. Genesis 8:3 then says the waters receded after that period. This figure describes the time the waters remained dominant, not the forty days during which rain fell and not the entire time Noah spent in the Ark.
The narrative uses several overlapping chronological markers. Rain begins in the second month of Noah’s six-hundredth year, the waters rise, the Ark comes to rest, mountain tops become visible, and Noah eventually leaves after the ground dries. These stages explain why different numbers appear in summaries of the Flood.
Readers sometimes treat 150 days as the total Flood duration, but Genesis continues its calendar through the recession and drying of the land. The safest precise answer is therefore “150 days” for the period in which the waters prevailed, matching the wording of Genesis 7:24.