In the biblical Noah's Ark story, how long did rain fall during the Flood?

In the biblical Noah's Ark story, rain fell for 40 days and 40 nights during the Flood.

Genesis 7 describes rain beginning after Noah, his family, and the animals entered the ark. The repeated period of 40 days is a major feature of the narrative and is also associated with periods of testing or transformation elsewhere in the Bible.

The 40-day rainfall is not the same as the entire duration of the Flood. Genesis also says that the waters prevailed on Earth for 150 days, and the broader sequence—from the start of the rain until the ground became dry—lasted much longer. This distinction is a common source of confusion.

The Genesis account is one of several ancient flood traditions, including the Mesopotamian stories of Atrahasis and Gilgamesh. Those stories also feature a great flood, a boat, and preserved life, but their characters and details differ.