Drizzle

Drizzle is an Ability introduced in Generation III.

Prior to Generation V, it was the signature Ability of Kyogre.

In battle:
Drizzle summons rain in as soon as a Pokémon with Drizzle enters the battle. Its effects are the same as the move Rain Dance, but instead of lasting for a limited amount of turns, it lasts for the whole battle (unless it is replaced by another type of weather).

If a Pokémon with Drizzle is sent out in the same turn as another Pokémon whose Ability affects the weather, the slower Pokémon's Ability will override the faster Pokémon's Ability.