The Sky High Pokémon, Rayquaza is similar to a cryptid atmospheric beast, spending the majority of its time flying above the clouds in the ozone layer, and appears as a meteor to those on the ground. As such, few have seen this legendary Pokémon. Rayquaza has the ability to negate all weather effects, and is one of the most powerful Pokémon in the franchise. Rayquaza has proven a popular character true to the spirit and concept of the games.

As with all the characters introduced in Pokémon Ruby and Sapphire, Rayquaza was designed by Ken Sugimori with the help of a development team. The name "Rayquaza" comes from a combination of the words ray and quasar. Rayquaza resembles a large serpent dragon. The design seems to be influenced by Mesoamerican art,especially that of Quetzalcoatl, the massive feathered green serpent of the skies.

Rayquaza is a dual type Dragon/Flying Pokémon. It has an elongated, green serpent body with yellow patterns covering its length. Red-tipped fins extend from its body in groups of three, and additional wing- or rudder-like appendages lengthen from a serpent-like head. Sharp, conical teeth line its mouth and some appear to be covered by gum tissue, similar to a Komodo dragon's. It lacks back legs, but has two arms with three white claws. Its tail is tipped with two small red-edged fins.

Rayquaza is the master of the weather trio, a group of three Pokémon who have control over weather conditions: itself, Kyogre, and Groudon. It is able to negate all weather conditions.Rayquaza lives far above the ozone layer, and is only very rarely sighted. Rayquaza eats water particles from the sky where it lives,and only descends when it wants to rest or if its fellow weather Pokémon, Kyogre and Groudon engage in combat. From the ground, Rayquaza appears as a meteor in the sky.