ORIGINAL: stang
Well I have flown at -40 degrees and the engines ran great. We usually held them under a car exhaust for a few minutes first and changed batteries every flight. It can be done but I honestly wouldn't fly in that cold again. We did it mainly to have some bragging rights on our buddies but it is terribly cold!
That is bragging rights, and nuts, I have flown around 0 and that is cold enough.
Jon