Winter has stripped the trees bare, and the poem lets a squirrel speak about it. At first the scene seems sleepy and cold: the tree is "stiff," "bleary-eyed," full of "old voices," as if it hasn't yet woken up. The squirrel rubs against the bark and tells it to wake up, and from there the mood shifts. Bare branches stop looking empty and start looking like open routes. Every gap can be crossed, every twig might hold something to eat.
The squirrel feels itself turning into rain and wind, moving through the treetops with restless energy. That energy seems to pass into the tree and into the season itself, which suits a poem about the new year. The last lines hold two feelings together: the "aching blue sky of January" is beautiful and a little painful, and "cries of thirst" suggest a hunger for what's coming. The mood is hopeful, but it is a hope that comes from wanting something.