The appearance of winter

Winter appears to have arrived. It has taken the form of a skimpy layer of frozen granular snow and temperatures in the teens, perhaps dipping to the single numbers tonight. Mary Roy of North Street is well into her second winter of four season gardening, with a new high tech cold frame and a thriving crop of mustard, lettuce and other greens. They have thrived in the season's warm weather, though they do not grow when the light is low from November to early February. It remains to be seen whether they will survive the new cold temperatures. The lettuce is just scrumptious looking.
Is it winter, or only the appearance of winter?