In the Book of Genesis, how many days did rain fall during Noah's Flood?

In the Book of Genesis, rain fell during Noah's Flood for 40 days and 40 nights. This duration appears in Genesis 7:12, describing the beginning of the flood after Noah, his family, and the animals entered the ark.

The number 40 has recurring importance in biblical narratives. Other examples include Moses spending 40 days on Mount Sinai and the Israelites' 40 years of wilderness wandering. In the flood story, the rain is only one part of a longer sequence: the waters later remained high before beginning to recede.

The phrase is sometimes mistakenly treated as the total length of the Flood. Genesis gives additional time periods, including 150 days during which the waters prevailed and the later stages of the ark's resting and Noah's departure. Thus, 40 days and 40 nights specifically describes the rainfall, not the entire episode.