Yeah I wouldn't pull just yet 40 or 50 degrees isn't that bad at all. Once you get below 30F for more than a night I would pull them. I am in Northern Canada and still haven't pulled anything yet, I'm at 46N. We had a night of -6celcius, where everything completly froze and I mean bad, like skating rink style. My girlfriends flower pots in her yard were all frozen solid (soil and roots), but amazingly the green is still thriving, so anyway you don't need to worry about anything above 30F. Mold may be a prob if it's always damp though.