According to Genesis, the floodwaters prevailed on Earth for 150 days during Noah's Flood.
Genesis 7:24 states that the waters prevailed for 150 days after rising over the land. This figure follows the account's statement that rain fell for 40 days and 40 nights, showing that the narrative distinguishes rainfall from the later period in which the waters remained dominant.
The chronology continues with the ark coming to rest on the mountains of Ararat in the seventh month. In the tenth month, the mountain tops became visible, and Noah eventually left the ark after receiving God's instruction. These dated stages make the story more elaborate than the familiar short summary.
Readers sometimes answer 40 days because that is the best-known number associated with the Flood. In Genesis, 40 days describes the rain, while 150 days describes the period during which the waters prevailed.