Room temperature and Humidity

I live in the great southern swamp called Florida. Humidity is our motto. More the merrier.
For standard filament (PLA, ABS) if it gets 'wet' (absorbs moisture) it will still print structurally fine. However there will be some micro surface defect that are caused by the steam bubbles. It is more of a visual thing than structural. Paint easily obliterates it.

Other filaments (nylon -- I am looking at you) easily absorb moisture and in that case (nylon) it can affect the print structurally if it is really, really wet. Even then it normally just makes a lot of popping noises while printing and usually still works, but fine details can be an issue (worse with smaller nozzles--less than 0.4).

Some other materials don't seem to care about or absorb much moisture. I don't bother trying to keep mine dry any longer (other than Nylon -- I keep it in a bag with desiccant). Prints come out OK and I have used just about every filament type.

 

The temperature issue might be more of a challenge. I probably have about the same temperature or less in my shop in the winter. PLA does OK with a heated bed, but anything else needs an enclosure.

It is industry best practice to keep plastics dry prior to processing, but I agree with Mark from a practical perspective. Aside from nylon, PC, and PVA (the latter two are not used by many because the moisture issues are so challenging) moisture issues are way overblown. ABS will get little bubbles in it if it absorbs moisture. It's easy to see and easy to resolve if you bake it out.

As far as PLA goes, I've been running these little make robots lately and using up my bits and pieces of filament. This guy was printed with some PLA/PHA that had been sitting on a shelf without any kind of bag or drying for over 2 years. Printed beautifully. These were printed 4 at a time with no stringing between whatsoever

 

Great catch. I seldom use those and totally waffled on remembering that. YES they are problematic wet.