Delta Stream is an Ability that was introduced in the Generation VI games Omega Ruby and Alpha Sapphire. This Ability is exclusive to Mega Rayquaza, and introduces a new Weather Condition to the series.
After becoming Mega Rayquaza, Strong Winds will kick up on the battlefield. Other weathers cannot be activated, and all other Weather Conditions are overriden, including Primordial Sea and Desolate Land, which cannot be removed otherwise.
The effectiveness of moves that would be Super-Effective on Flying-Type Pokémon are also removed. This weather condition will persist until Mega Rayquaza is no longer in the battle.
Delta Stream doesn't have an effect in the Overworld.
Pokémon With This Ability