I would not 3D print... as @PaulRB said, there are materials resisting to weather... Polycarbonate, Fiberglass, Aluminum, Stainless Steel, ABS Plastic... the latter is commonly used for outdoor electrical enclosures and cases you'll likely find in your neighbourhood.
PS/ if that's not enough then you can apply Epoxy or Polyurethane Coatings and there are UV-Resistant Paints too.
UV has enough energy to cause the polymers in plastic to disentangle. This is especially rapid in colored plastic because they are just a mixture and not really joined together with the base polymers. Most coloring plastic is of unknown origin.
So, first, if you use plastic only use known polymers that resist UV and known coloring that resists UV.
Second, use paint/coatings that the automotive and marine industries use that will protect from UV damage.
A datasheet for one particular OLED display i have is very clear that it must not be exposed to direct sunlight. No mention if it's because of UV damage, heat, or both. I plan to use tinted film, it will take care of both possibilities.