As spotted by Fortnite dataminer FortTory, the posters appear to have been added in the latest Fortnite patch notes as part of the v.12.40 update. According to FortTory, the posters are called "S13_poster_Teasers!\", which does suggest that these posters could be teasing an event or change to the map in the new season.
The posters show one of the more recent character additions Meowscles wearing swimming armbands in a body of water that rises up to their waist. Along with the muscle-bound cat, the other posters feature a house in a lifebuoy ring and Peely in a rather perilous situation swimming above a very big shark. Oh, no. Watch out, Peely.
These are called: S13_Poster_Teasers!\OUIR FIRST TEASERS FOR SEASON 13 pic.twitter.com/FpvKv8xrdxApril 29, 2020
The posters definitely seem to hint at some kind of water-related event, or perhaps even disaster that leads to parts of the map being flooded or perhaps altered. Curiously the posters feature the flaming umbrella logo for the No Sweat Insurance company, and if a flood is on the way, it'd make sense to snap up some insurance for it. We don't know how the map might flood, but there are plenty of areas on the map that could flood to change up the landscape temporarily, or perhaps permanently.
Chapter 2 Season 3 was originally set to go live at the end of April before it was eventually pushed back to June. The current season is expected to run throughout May with a month extension for Season 2, so it'll be quite some time before we find out just what these posters are teasing. With the latest Tyler Scott Astronomical event, Epic has proven time again that Fortnite is full of surprises, so anything could happen.
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