Because there are no human beings in this story—they have all been killed in a nuclear holocaust—Bradbury personifies the house and nature.
At the end of the story, Bradbury personifies the fire, a symbol of nature's power. He depicts it as a force stronger and smarter than the highly technological home. We learn that
the fire was clever. It had sent flames outside the house, up through the attic to the pumps there. An explosion!
Cleverness, described here as the ability to think strategically and plan a knock-out blow, is a trait with associated with human beings, not fires.
The fire is also described as "angry"; anger is an emotion we associate with humans.
The fire is connected thematically to the Teasdale poem which gives the story its title. In the poem, nature placidly and indifferently goes about its business whether humans are on the earth or not—it is shown as a force more quietly powerful than human technology. The fire is not quiet or indifferent, but it is more powerful than human technology (it destroys the house), and it is indifferent to the value humans place on the objects it destroys.
The personification of the fire also lends an energy and a personal quality to the end of the story that otherwise might not be there.