Do I leave things outside, or do I have to bring them in?
What structures you leave outside depend on how well the item will withstand the elements. Most products manufactured for large-scale railroading are intended to be outdoors. However all of these items will weather, fade, warp, rust or mold over time. The rate of wear directly relates to your local weather. The trains themselves usually are less tolerant of the elements and should not remain outdoors for extended periods.