In the Genesis account, the floodwaters prevailed over the earth for 150 days.
Genesis 7:24 states that the waters prevailed for 150 days. This figure is distinct from the 40 days and 40 nights of rain described earlier in the narrative. The text presents the rainfall and the longer period during which the waters remained dominant as related but different time spans, so they should not be treated as interchangeable.
The story later says that the waters began to decrease, and the ark came to rest in the seventh month. Genesis then describes additional waiting periods before Noah removed the covering and eventually left the ark. Because the account uses ancient calendar references and includes several separate intervals, readers can reach different totals when reconstructing the entire chronology. The specific statement about the waters prevailing, however, is 150 days.