Snow Warning is an ability introduced in Generation IV. So far, 4 Pokémon have this ability.
Snow Warning creates a Hailstorm (like the one from move Hail) when the bearer enters battle. The effect lasts 5 turns (8 if the user is holding an Icy Rock,) unless it is cleared via Cloud Nine or replaced by another weather condition.
If multiple Pokémon with weather-generating abilities (Snow Warning, Drizzle, Drought, Stormbringer or Sand Stream) enter the field on the same turn, the slowest Pokémon's ability will be the last to activate.
Outside of battle
Snow Warning has no effect outside of battle.
Pokémon with Snow Warning