In the biblical account, God set a rainbow in the clouds after Noah's Ark and the Flood.
Genesis 9 presents the rainbow as the sign of a covenant between God, Noah, his descendants, and every living creature. The covenant promises that a flood will not again destroy all life on Earth. Whenever the rainbow appears in the clouds, the text says, it serves as a reminder of that promise.
The passage places the sign after Noah and the animals leave the Ark. Noah builds an altar, and the story then describes the covenant and its visible sign. The rainbow therefore functions in the narrative as a symbol of remembrance and restraint, not merely as a weather observation.
The account also broadens the covenant beyond Noah's family by explicitly including the animals and the earth.