From the facts presented here I can conclude that USPS Priority mail (or express mail) is the safest way to ship CPs during the winter.
Matt has the best evidence:
"Steve and I have shipped probably over 100 orders during the winter months via USPS Priority Mail and we've not yet had one customer report that the plants were frozen upon arrival."
Matt has the best evidence:
"Steve and I have shipped probably over 100 orders during the winter months via USPS Priority Mail and we've not yet had one customer report that the plants were frozen upon arrival."