When a Pokemon with Delta Stream enters the battle or a Pokemon gains the Ability Delta Stream, the Ability creates strong winds, a unique weather condition. The strong winds last as long as the Pokemon with Delta Stream is in battle with the Ability. In a Rotation Battle, Delta Stream will not activate if the Pokemon is sent out in a rotated-out position and will not activate if the Pokemon is rotated in; the strong winds will dissipate if the Pokemon is rotated out.
Strong winds cause moves that would be super effective against pure Flying type Pokemon to instead deal neutral damage to all Flying type Pokemon. Outside of Inverse Battles, this causes Electric-, Ice-, and Rock type moves to deal neutral damage to Flying type Pokemon; during Inverse Battles, this causes Bug type, Fighting type, Grass type, and Ground type moves to deal neutral damage to type Pokemon. If a move is not super effective against the Pokemon’s other type (for dual typed Pokemon), this no longer counts as a super effective hit (for the purposes of damage-reducing Berries, etc.). Strong winds have no effect on Stealth Rock or Anticipation.
Additionally, strong winds cause the weather modifying moves Sunny Day,Rain Dance, Hail and Sandstorm to fail if used; and they cause the Abilities Drought, Drizzle, Sand Stream and Snow Warning to fail to activate.
If Delta Stream is suppressed or replaced, the strong winds it causes will disappear. If another Pokemon in battle has the Ability Desolate Land orPrimordial Sea, the dominant weather condition will be determined by whichever Ability activated last.
Outside of battle
Pokemon with Delta Stream