When Mega Rayquaza whips up strong winds with its Delta Stream Ability, this is what happens:
- The moves Rain Dance, Sunny Day, Sandstorm, and Hail will fail.
- The Abilities Drizzle, Drought, Sand Stream, and Snow Warning will fail to activate.
- Moves of a type that Flying-type Pokémon are usually weak to
will only deal normal damage to any Flying-type Pokémon in the battle.
Also, with Delta Stream, weather effects last indefinitely as long as Mega Rayquaza remains in battle. When it is swapped out for another Pokémon on your team, the weather immediately returns to normal.
This is different than the Abilities Drizzle, Drought, Sand Stream, and Snow Warning, which can all affect the weather for five turns after being activated in battle, regardless of whether the Pokémon with these Abilities are still in battle or not.
The Delta Stream Ability and the Air Lock Ability are different in that Delta Stream fills the air with strong winds for as long as Mega Rayquaza remains in battle. Air Lock cancels out all weather-condition effects for all of the Pokémon in a battle as long as Rayquaza remains in the battle.