To successfully complete the "visit the Snowmando Outposts locations" challenge on Fortnite, all you have to do is go to these outposts and set foot on the ground, your quest progress bar should fill up in real time to confirm that the outpost you are in has indeed been counted.
Outposts are red buildings with planes next to them. They are decorated in Christmas colors, are usually filled with gifts, and can be found all over the map.
Warning: whether it's a bug or a feature wanted by epic, not all outposts will appear in all games.
Outpost locations
Since not all outposts seem to appear every time a game is started, you may need to play multiple games to complete your challenge. Either way be aware that outposts are a decent place to start a game, each of them will likely contain multiple chests and a plane to rotate to any location on the map.
Original content by Augustin "Review" Heliot.
