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 Fake Straw Hat Crew, launching a miniature lightning storm to electrocute them, thus turning the Weather Balls into a weapon that she asked Haredas about two years ago.