We flew last winter down to -25C/-13F. Wind doesn't make any temp difference to the plane because it cools down to the air temp anyway.

The Rx batteries only lasted for a flight or two (so did my fingers), but the engine and radio gear worked well. My only problem was that the Monokote became brittle. I put my finger through the wing when I tried to lift the plane. Other than that it was quite fun. I know that Futaba specify -10C as minimum operating temp for some of their radio equipment, other manufacturers might have similar temp limitations...?