In Genesis, the Flood waters prevailed on Earth for 150 days.
Genesis 7:24 states that the waters prevailed upon the earth for 150 days. This duration follows the account of rising waters and is longer than the 40 days and 40 nights during which rain fell. The two numbers describe different portions of the narrative.
Genesis then describes the waters gradually receding. The Ark came to rest on the mountains of Ararat, and later observations involving a raven and a dove marked the changing conditions outside the vessel.
The chronology of Genesis contains several overlapping time references, and different translations or readings can make the sequence difficult to summarize. The 150-day statement itself is explicit in Genesis 7:24. It should not be presented as the total period from entering the Ark to leaving it, because the narrative continues after the waters stop prevailing.