Even though the air temperature was well below 0F for most of the day, the squirrels were out looking for goodies. Unlike their usual ground foraging activity, today their efforts seemed to be restricted to the trees. Something I have never seen these squirrels do before: flatten themselves against the tree and sit still for several minutes at a time. I think they must have been trying to pick up some heat from solar radiation.
I couldn’t find much in the science literature about basking behavior in gray squirrels, but there are other species of squirrels that definitely use this strategy to reduce metabolic costs in extreme cold weather. Rather than remain inactive in their nest, the squirrels have opted to utilize whatever warmth the weak sunlight provides and hope they can remember where they stashed a few of their nuts for a quick snack.