In the Genesis account of Noah’s Ark, the Flood waters prevailed for 150 days. Genesis 7:24 gives this figure after describing the rising waters and the destruction of life outside the Ark.
This 150-day period is not the same as the 40 days and 40 nights of rain. Genesis first describes the rain, then records the waters prevailing, and later narrates their gradual recession. Keeping these intervals separate prevents one of the most common numerical mix-ups in the story.
The chronology continues with the Ark coming to rest on the mountains of Ararat in the seventh month. Genesis then describes the mountain tops becoming visible and Noah waiting before leaving the vessel.
Translations can vary slightly in wording, but the standard English rendering of Genesis 7:24 is 150 days. The number is a duration in the narrative, not a measurement of the Ark or a calendar year.