According to Genesis, God set a rainbow in the clouds after Noah’s Flood.
Genesis 9:13 describes the rainbow as the sign of God’s covenant with Noah, his descendants, and every living creature after the waters had receded. Whenever the rainbow appeared in the clouds, it would recall that covenant.
The covenant promises that a flood would not again destroy all flesh and that the earth would not again be devastated by such waters. The sign is therefore connected to a promise concerning the future, not merely to the weather event that ended the Flood.
Genesis places the rainbow after Noah leaves the Ark and builds an altar. The passage is sometimes summarized as God promising never to send rain again, but that is not the precise wording: the covenant concerns the destruction of all life by a flood. The rainbow is the visible sign of that broader promise.