Drought is a Generation III ability that causes the Clear Skies weather effect when the Pokémon enters battle and strengthens the attack of a Fire-type Pokémon. SolarBeam does not need to be charged in Clear Skies. Drought stays in effect for as long as the Pokémon wielding it remains in battle. If that Pokémon is no longer in battle, the effects will linger for a few more turns. As of Pokémon X and Y, it only last 5 turns.