After becoming Primal Kyogre, a very Strong Rain will start to fall. The main difference between this and Drizzle is that the weather is locked into Strong Rain and cannot be changed by another Pokémon's moves or Abilities. Furthermore, Fire-Type moves won't have any effect, and the weather condition will last as long as Primal Kyogre remains in battle.
Primordial Sea doesn't have an effect in the Overworld.
Pokémon With This Ability