Weather Ball is the most important invention on Weatheria.
Nami stole one of these inventions and it is later seen when she returns to Weatheria and asks Haredas how the Weather Balls work and if they can be turned into a weapon. Haredas is horrified at this thought and tells Nami not to say such scary things since the Weather Balls are capable of causing chaos around the world.
The Weather Balls can also be used to store little pieces of clouds in them. When a few Weather Balls with clouds are combined, a big cloud is formed. The cloud can also shoot lightning. Nami used such a feature to attack the Impostor Straw Hat Pirates, launching a miniature lightning storm to electrocute them, thus turning the Weather Balls into a weapon that she asked Haredas about two years ago.
- Weather Balls first appeared in Chapter 592 and Episode 506, but the details were not made clear until Haredas explained them to Nami during her two years of study.
- ↑ 1.0 1.1 1.2 One Piece Manga and Anime — Vol. 60 Chapter 592 and Episode 506, Weather Balls are first seen but not introduced.
- ↑ 2.0 2.1 One Piece Manga and Anime — Vol. 61 Chapter 596 and Episode 514, Haredas introduces Weather Balls to Nami.
- ↑ One Piece Manga and Anime — Vol. 61 Chapter 598 and Episode 517, Nami uses Weather Balls to electrocute the Impostor Straw Hat Pirates.