When it started getting quite cold here a couple weeks ago, the freewheel on my singlespeed started acting wonky. The chain would only "grab" at certain spots in the rotation of the freewheel. I'm guessing that there might have been something that froze up the pawls. After a few days it got better, though it did not get any warmer. Whatever the frozen problem was, it was temporary. Yesterday morning it was -4F here. I was fine temp wise, except for my toes after about 45 minutes. Coldest windchill I have ridden in was around -25F. Again, that didn't really make me cold.