When does the lake of rage flood in Pokemon HeartGold and SoulSilver?

The Lake of Rage doesn't flood in Pokémon HeartGold and SoulSilver. It's always in a flooded state.

The flooding of the Lake of Rage is a plot point in the original Pokémon Gold and Silver games, where you need to help the Legendary Pokémon Lugia calm the lake and stop it from flooding. This plot point is absent in HeartGold and SoulSilver.