Generation Iv
Snow Warning
The Pokémon summons a hailstorm in battle.
Detailed Effect
The weather changes to hail when this Pokémon enters battle and does not end unless cancelled by another weather condition. If multiple Pokémon with this ability, Drizzle, Drought, or Sand Stream are sent out at the same time, the abilities will activate in order of Speed, respecting Trick Room. Each ability's weather will cancel the previous weather, and only the weather summoned by the slowest of the Pokémon will stay.
Pokémon With Snow Warning
9 canonical Pokémon forms can have this Ability.

Snover
Abomasnow
Vanilluxe
Mega Abomasnow
Mega Froslass
Amaura
Aurorus
Alolan Vulpix
Alolan Ninetales