We have -11C (or thereabouts) air over the region nearly 2 weeks ago... with clear skies and very little wind, the lowest temperature here was -3C. No snow that time true enough, but having said that, with the GFS showing maxes after the weekend of 4-6C here every day, it doesn't really warrant that type of minima. If we were in january though, I'd agree -7 or lower would be possible.