Ray Bradbury no doubt placed the setting for his 1954 short story “All Summer in a Day” on Venus because of the centrality of atmospheric conditions to his story of a nine-year-old girl and her classmates eagerly awaiting a rare display of the Sun.  Admittedly, the same objective could have been attained by placing the story in Seattle, but, Bradbury being a science fiction writer, he chose Venus instead.  Early in his story, he establishes the setting as follows:

“It had been raining for seven years; thousands upon thousands of days compounded and filled from one end to the other with rain, with the drum and gush of water, with the sweet crystal fall of showers and the concussion of storms so heavy they were tidal waves come over the islands. . . And this was the way life was forever on the planet Venus, and this was the schoolroom of the children of the rocket men and women who had come to a raining world to set up a civilization and live out their lives.”

While knowledge of Venus’ atmosphere was extremely limited in the early 1950s – the Mariner 2 probe wouldn’t approach that planet’s atmosphere until 1962 – enough was known about both its and Mar’s respective atmospheres to make it a more viable candidate for a story in which exposure to direct Sun light is a rare and precious commodity.  Venus has an extremely opaque atmosphere and is known to rain constantly.  Lacking detailed knowledge of the composition of its atmosphere, though, Bradbury couldn’t yet know that the rains that occur constantly on Venus are acid rains and not conducive to human habitation, or the growth of vegetation he describes (“the great jungle covering Venus”), even with the inhabitants residing in an underground city. 

In addition to the role of rain in establishing mood and atmosphere for the planet on which the story takes place, Bradbury extends the metaphor to his lead character, Margot,

“a very frail little girl who looked as if she had been lost in the rain for years and the rain had washed out the blue from her eyes and the red from her mouth and the yellow from her hair.”

  The depressive component of continuous rain is carried through to Margot’s breakdown in the shower one day:

“. . . once, a month ago, she had refused to shower in the school shower rooms, had clutched her hands to her ears and over her head, screaming the water mustn’t touch her head.” 

While Margo’s plight – the only one of the children to have ever experienced sunlight and for whom the approaching break in the rain and clouds was a greatly anticipated event – is hardly central to the question being addressed, the focus on her emotional state, her intense hatred for falling water, is consistent with the choice in settings for the story – but only to the extent the story was placed on a distant planet known to experience intense and protracted precipitation.  The placing of the story on Venus appears to have occurred solely to both satiate the need for a science fiction writer to place a story in another world and to convey a sense of atmosphere “alien” to what inhabitants of most of the Earth experience during the course of their lives.  The setting could have taken place on a fictionalized Earth and accomplished the same objective.