Epic seems to have listened to community feedback and is keeping some snow in the Fortnite map.
Back when Fortnite Chapter 3, Season 1 first launched, dataminers dived into the game's files and found screenshots of the game's map over a period of time. These images implied that the snow that was covering most of The Island was slowly going to melt over the course of a few weeks, leaving a completely green and brown island with no other biomes in sight.
Although many Fortnite players don't like the snow covering all of the map, a good portion of the community agreed that at least some of The Island should have some so that it shouldn't all be green forest and canyons. It looks like Epic took that feedback on board, as the final version of the map no longer melts everything and instead keeps a good portion of the snow in the northwest area of the map, near Logjam Lumberyard.
This was pointed out by reliable Fortnite leaker Hypex, who posted a picture of the map on Twitter and said, "Epic changed the snow to stop melting at this stage in 19.10, looks like they listened and the snow is staying. I have no idea if it was intended but the snow won't melt anymore after this!"
Although the reappearance of Tilted Towers made it clear that Epic's plan was always to melt the snow to a certain point, considering the datamine showed the map being completely clear of it, but the community outcry after seeing those leaks might have caused Epic to listen and keep it from melting all the way. The current amount of snow on the map was also shown in the datamine, implying Epic has just stopped it from going to the next stage.
As with anything in Fortnite, it's possible that this will change in the future and that Epic will continue to melt it at a later date, but for now it looks like the snow is staying.