In the biblical Noah’s Ark account, rain fell on the Earth for forty days and forty nights.
Genesis describes the Flood beginning after Noah entered the ark. Rain then fell continuously for forty days and forty nights, while the waters rose and covered the land. This period describes the rainfall itself, not the entire time Noah and the animals remained aboard the ark.
A common mix-up is confusing forty days of rain with the total duration of the Flood. Genesis also says that the waters prevailed for 150 days, and the complete episode lasted much longer before the ground became dry. The forty-day figure is therefore one stage in the story’s chronology.
The number forty has wider biblical significance, appearing in other periods of testing or transition, including Moses’ time on Mount Sinai and Jesus’ fast in the wilderness. The Qur’an also recounts Noah, but its account does not present the same detailed forty-day rain formula.