How many days and nights of rain does Genesis describe during the Flood?

Genesis describes rain falling for forty days and forty nights during the Flood.

Genesis 7:12 uses the well-known phrase “forty days and forty nights” for the period of continuous rain. In the narrative, Noah, his family, and the animals are already aboard the ark when the rain begins. This period is not the same as the entire duration of the Flood event.

The same account says the waters prevailed for 150 days, and Genesis 8 records the later recession of the waters. Thus, readers should distinguish the forty days of rain from the longer interval during which the Flood remained high. The story also says Noah waited for additional periods before leaving the ark.

The number forty has wider significance in biblical literature, where it often marks an extended testing or transition period. In this passage, however, the specific statement concerns rainfall. It does not mean that the rain lasted only forty days from the beginning of the catastrophe to the moment the ground became dry.