It should be noted that Ray Bradbury, across his entire writing career, was a very imagery-intensive writer. "All Summer in a Day" is hardly unique in this respect. Whether one is speaking about novels like Fahrenheit 451 or Something Wicked This Way Comes, fix-up novels such as The Martian Chronicles, or so many of his innumerable short stories, you will tend to find that same richly lyrical quality almost continuously present.
We see this in Bradbury's description of the planet Venus itself, with its heavy, unceasing rainfall (and Bradbury's evocative description of that rainfall), but his descriptive powers conjure a deeply visual impression of the planet's alien jungle as well:
They stopped running and stood in the great jungle that covered Venus, that grew and never stopped growing, tumultuously, even as you watched it. It was a nest of octopi, clustering up great arms of fleshlike weed, wavering, flowering in this brief spring. It was the color of stones and white cheeses and ink, and it was the color of the moon.
This description is joined by the description of the children playing within this jungle and feeling a shared sense of awe at the experience of being outside.
Like in so much of Bradbury's work, imagery appears to be almost omnipresent. In addition to his description of Venus itself, you can observe its use in his description of Margot, thin and frail, almost ghostlike in her quiet somberness:
She was an old photograph dusted from an album, whitened away, and if she spoke at all her voice would be a ghost. Now she stood, separate, staring at the rain and the loud wet world beyond the huge glass.
Bradbury thus uses imagery to convey the essential truths both his setting and the characters that inhabit it: in Margot's case, both her sense of isolation as well as her longing for the sun are primarily driven and advanced through the images Bradbury conjures regarding her, as we can observe in a passage like the following:
And this was because she would play no games with them in the echoing tunnels of the underground city. If they tagged her and ran, she stood blinking after them and did not follow. When the class sang songs about happiness and life and games her lips barely moved. Only when they sang about the sun and the summer did her lips move as she watched the drenched windows.
Bradbury tended to seek to use imagery with the aim of making his worlds and characters come to life in the imaginations of his readers. This imagery-focused and highly lyrical approach to prose is one of the central characteristics that defines his authorial voice.