Genesis says the Floodwaters prevailed over the earth for 150 days. Genesis 7:24 gives this figure after describing the rising waters and their effect on the land.
This number is distinct from the 40 days and 40 nights of rain. The rainfall describes the period during which rain fell, while the 150 days describes the longer period during which the waters remained dominant. Genesis 8 then begins the account of the waters decreasing.
The chronology includes several dated milestones, including Noah’s entry into the Ark, the Ark’s resting on the mountains of Ararat, and the later emergence of dry land. Interpreters have examined how these dates fit together, sometimes using different calendar assumptions.
The figure is therefore best understood as a specific duration stated in the Genesis narrative, not as a claim that rain continued nonstop for 150 days. Confusing these two numbers is one of the most frequent factual errors about the story.