Depends, of course, where in NC. I'm just south of Charlotte and it got to 8 degrees measured but much lower with wind chill. Best part here is the cold is not continuous. A few days in a row. I'm referring to the polar vortex events (we had 2).

Generally, it's rather rare to be in the single digits here in 7B-8A planting zone.

As worrisome as the extreme cold is the increase of triple digit heat waves. That really impacts vegetable production and ripening no matter how much rain water is available.

Being on the less extreme weather side of the the App. Mountains and far enough from wide rivers and major highways makes for more temperate, calmer weather events.

We discussed the historical data for the Raleigh-Durham area around the January 2014 cold event in this thread: historical minimum temperatures for RDU .

More recent information can be viewed as monthly summaries (up to 5 years) in Observed Weather Reports from the National Weather Service for any weather station, for example Raleigh again: see the Preliminary Monthly Climate Data (CF6) product.

Longer-term data can be downloaded from the National Climatic Data Center, another unit of NOAA: Climate Data Online

Okay so there were 3 times in many years that Raleigh- Durham went to 0F? Then there were some 10F (roundabouts)? I am hoping that I saw the chart right. I tried my magnifying glass, over 40 years old here. Thanks Casa