https://www.polygon.com/fortnite/2018/8/24/17778070/fortnite-lightning-h9-countdown

Fortnite’s meta-story of events and characters that impact the game’s map is heating up again, as the rifts in the sky have begun to spit out lightning bolts that hit the ground on square H9 on the map. Fans now think it could all be leading to an in-game event that’s taking place later today.

Players first noticed the lightning strikes yesterday, with streamers witnessing a few while they were broadcasting gameplay.