In Genesis, how many days and nights did rain fall during the start of the Flood?

In Genesis, rain fell for 40 days and 40 nights at the start of the Flood.

Genesis 7:12 states that rain fell upon the earth for forty days and forty nights. This is different from the longer periods used elsewhere in the narrative. Genesis says the waters prevailed for 150 days, while the complete chronology describes a much longer interval before the ground became dry.

The number 40 is also prominent in other biblical narratives, including Moses’ time on Mount Sinai and Israel’s wilderness period. In biblical literature, forty often marks an extended testing, transition, or preparation period, although the Flood account also uses it within a sequence of specific chronological statements.

The rain’s 40-day duration should not be confused with the total duration of the Flood or the time Noah waited before leaving the Ark.