How long did Genesis say the rain fell during the beginning of the flood?

Genesis says the rain fell for forty days and forty nights at the beginning of the flood.

Genesis 7:12 states that rain fell upon the earth for forty days and forty nights. Genesis 7:17 repeats the forty-day period in describing the rising waters and the ark being lifted above the earth.

The number forty is not the whole duration of the flood episode. Genesis also says that the waters prevailed on the earth for 150 days, and the broader chronology includes later waiting periods before the ground became dry. Because these numbers describe different stages, “forty days” should not be treated as the time from the flood’s start until Noah left the ark.

Forty is a recurring time period in biblical narratives, appearing in stories involving testing, travel, and preparation. In the ark account, its most direct meaning is the initial period of sustained rainfall. The separate 150-day figure refers to the dominance of the waters, not simply to rainfall.