How does the setting help establish the main conflict in the story "All Summer in a Day"?

The incident could not have happened anywhere other than Venus because the children bullied Margot for having seen the sun.

The setting of the story is Venus.  It rains all of the time on Venus, and the sun has not come out in seven years.  Margot is from Earth, so she has seen the sun.  No one else in her class has seen it since the age of two.

It had been raining for seven...

The incident could not have happened anywhere other than Venus because the children bullied Margot for having seen the sun.

The setting of the story is Venus.  It rains all of the time on Venus, and the sun has not come out in seven years.  Margot is from Earth, so she has seen the sun.  No one else in her class has seen it since the age of two.

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.

The conflict is the children’s distrust and bullying of Margot.  They put her in a closet when the sun was about to come out.  It was a silly prank, and they really did not mean anything by it.  They felt awful when they were done and Margot felt terrible because she missed the sun, and it would be years before it came out again.

A story’s setting affects the conflict because conflicts result from the setting and characters.  In this case, the characters are nine-year-old kids.  They live on Venus, and it rains on Venus constantly.  This is part of the setting because the absence of the sun is the status quo.  If the story had taken place on Earth, the children might have bullied Margot, but for other reasons. 

They edged away from her, they would not look at her. She felt them go away. 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.

She did not fit in.  However, the reason for her not fitting in might have been different if the story had taken place on Earth.  In that case, the story still would have been different because there would be another reason for Margot’s alienation.