https://www.gamespot.com/articles/fortnites-countdown-lead-to-a-tear-in-the-sky/1100-6460118/

We've been seeing Fortnite's countdown tick for a while now, and it finally hit zero. Today's event was the launch of the rocket in Anarchy Acres, and it's left a tear in the sky.

Fortnite's countdown was to a one-time event, a rocket launch. We've speculated that it might have something to do with Season 5. Season 4 began in a similar way with the impact of the meteor, and so far, we know Season 5 has been teased with a mysterious siren.