Genesis says Noah’s Ark came to rest on the mountains of Ararat after 150 days.
Genesis 7:24 states that the waters prevailed over the Earth for 150 days, and Genesis 8:3–4 says that they receded after those 150 days, with the Ark coming to rest in the seventh month. The account therefore distinguishes the period of prevailing waters from the 40 days and nights of rain.
This timeline is easy to compress incorrectly. The rain lasted 40 days and 40 nights, but the floodwaters continued to dominate the landscape much longer. Genesis then records additional waiting: the mountain tops became visible in the tenth month, and Noah waited through several further intervals before leaving the Ark.
The dates in the narrative are given using months and days of Noah’s six-hundredth and six-hundred-first years, producing a detailed chronology rather than a single brief storm.