Found this article informative and figured this would be a good place to share it.
Also found this bit very interesting:
“Cold hardiness” is a vague and often misleading term because low temperature injury can vary depending on when the low temperatures occur (early vs. mid or late winter), how fast the temperature drops, what the temperatures were during the previous few days, and how long the low temperatures are sustained. For this reason every cold event is fairly unique and a plant may be affected differently by different cold events.
For example, the peach rootstock ‘Siberian C’ survives sub-zero temperatures in Ontario where winter temperatures are consistently low, but it is winter killed at above zero temperatures in the South where winter temperatures fluctuate. So ‘Siberian C’ is considered “cold hardy” in Ontario, but not in South Carolina.