Three short lines give us two pictures: a landscape full of autumn color, and one yellowjacket flying badly. The poem never says how the speaker feels, but the choice of detail does the work. Fall colors are usually a celebration of beauty, yet they are also the sign that something is ending. The yellowjacket's unsteady flight points in the same direction. Late in the season, insects often seem slow and worn out, and the poem suggests that this one is losing its strength as the weather turns.
The title, "Lookout," hints at someone watching, perhaps from a high place with a wide view. The speaker seems to notice the large scene and the tiny one in the same moment. The mood is quiet and a little wistful. There is admiration for the colors, but also a gentle awareness of fragility and the passing of time. Nothing dramatic happens, and that stillness is what makes the moment linger.