During the Real Life winter season, several SWRP sims add winter decorations. I recall Last year Taris snow filled the neighbourhood of the Furious shop, Bakura was filled by snow with a snowman contest organized by the GAR and Malachor V having a dead Christmas tree and some snow patches in the heart of the Trayus academy.
Zonama Sekot had its snow decoration, all the sim was changed with snow textures, the ground, the paths, the roofs and even the trees. The central lake was frozen and we organized skating. We had a similar but more improvised decoration two years ago.
I'll redo a similar background this year, the snow will progressively cover the sim for few days. During the holidays, many people are away or just pass few hours or even minutes and aren't much in a roleplay mood. It's the occasion to do something different.
For the in universe reason of having snow falling on a rainforest? Well, it's... because... it's snowing... right?