The rainbow is the sign of God’s covenant with the survivors of Noah’s Ark flood.
In Genesis 9, God establishes a covenant with Noah, his descendants, and every living creature that a flood will not again destroy all life on Earth. The rainbow is presented as the visible reminder of that promise. The passage places the sign in the clouds, linking it directly to the storm and the waters that have receded.
This covenant follows Noah’s departure from the ark and his offering. It is broader than a promise made only to Noah’s family: the text repeatedly includes living creatures and the Earth in the covenant’s scope.
A rainbow is an optical phenomenon produced when sunlight is refracted, reflected, and dispersed by water droplets. Genesis uses it as religious symbolism, while the scientific explanation describes how the colors appear. The story’s covenant sign is therefore specifically a rainbow, not another sky phenomenon.