According to local legend, long ago, a thunderstorm caused by the Legendary PokémonZapdos caused a large tree in the center of town to split in two. To the townsfolk's surprise, after being burnt by Zapdos's electricity, the tree grew taller than it even had before, and bore many fruit. Since that day, the people of Joule Town have held the Zapdos Festival, in the hopes that Zapdos would visit again to bless the town with good fortune. According to Clemont, the festival also celebrates Electric-type Pokémon.
In the episode, Ash and his friends made it to Joule Town just in time to watch the festivals opening fireworks display.