A walker moves quietly through damp woods early in the morning, and the only sounds come from the squirrels, which seem to be scolding him. The speaker's boots barely make a noise, so the animals' fuss feels a little sudden, as if the forest had been calm until something broke it.
The surprise comes in the last line. The speaker is startled too, because he can see his own breath in the air. That's odd for July, and the poem leaves us to guess why. The morning may simply be unusually cold, or the damp woods may hold a chill. Either way, the speaker feels the same jolt the squirrels do, and that puts him on their level rather than above them.
The mood is hushed, alert, and gently funny. Nothing dramatic happens, but the poem captures a small moment of seeing yourself as part of the natural world, just as strange and jumpy as everything around you.