In Genesis, how long did rain fall during the Flood before the waters rose?

In Genesis, rain fell for forty days and forty nights during the Flood.

Genesis 7:12 uses that phrase when describing the rain that fell on the earth after Noah entered the Ark. The chapter also says that the waters prevailed for a much longer period, so the forty-day rainfall should not be confused with the total duration of the Flood event.

Genesis 7:24 says the waters prevailed over the earth for 150 days, and Genesis 8 continues with the gradual recession of the waters. Thus, “forty days and forty nights” describes the rainfall period, not the entire time Noah and the animals remained aboard.

The number forty has wider biblical significance, appearing in other stories involving testing, preparation, or transition. Flood traditions from the ancient Near East also contain extended periods of rain or inundation, but their numbers differ. The answer here refers specifically to the Genesis account.