Drought summons harsh sunlight in battle as soon as a Pokémon with Drought enters the battle. Its effects are the same as the move Sunny Day, but instead of lasting for a limited amount of turns, it lasts for the whole battle (unless it is replaced by another weather condition). If a Pokémon with Drought 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.
The sunlight now lasts only for five turns. This can be extended to eight turns if the Pokémon is holding a Heat Rock.
In Super Mystery Dungeon, Drought changes the weather to sunny upon entering a floor. The sunny weather condition lasts a certain number of turns (in multiples of 66) before clearing. After the weather has cleared, Drought will again activate after waiting a certain number of turns (in multiples of 66).