After the flood, God set a rainbow in the clouds as the sign of the covenant in the Genesis Ark story. Genesis 9 presents the rainbow as a reminder of the promise that a flood would not again destroy all living creatures.
The covenant is made not only with Noah but also with his descendants and every living creature. In the biblical narrative, the rainbow therefore has a theological meaning: it marks a relationship and promise between God, humanity, and the living world.
The rainbow was not introduced as a weather explanation in the modern scientific sense. Its story function is symbolic and covenantal. In later cultures and religious traditions, the rainbow has acquired additional meanings, but the Genesis account specifically connects it with the post-flood covenant.