"All Summer in a Day" is a short story by science fiction author Ray Bradbury. This story was originally published in 1959 in a Bradbury short story collection entitled, A Medicine for Melancholy.

The story deals with a group of frolicking schoolchildren residing on a warm, tropical Venus that was colonized by "rocket men and women who had come to a raining world to set up civilization and live out their lives", at an unspecified time in the future. The thick atmosphere of Venus still exists at this time, and it is constantly raining, therefore seeing the sun is a very rare event, which occurs only every seven years for just one hour.

The story is mainly about Margot, a little girl who moved to Venus from Earth five years before the story takes place. She remembers the sun and the way it looked and felt. She doesn't play much with the other children in the underground city they live in and she is an outcast because of her sensitivity and the fact that it was rumored that she may return to Earth the next year. The kids are jealous of her because she remembers the sun but they were only two years old when it last came and don't remember it. She almost had a nervous breakdown from living with the relentless rain because she got too sick of it. For example, when she was supposed to take a shower at her school locker room but she refused to get wet. She clutched her hands over her head and screamed the water must not touch her head.

She writes a poem about the sun: "I think the sun is a flower that blooms for just one hour." She also describes it as "a penny" or a "fire in a stove". The other children don't believe her and the class bully, William, starts to harass her physically and verbally. While the teacher is out of the room, he convinces the other children to lock Margot in the closet.

The teacher finally comes back and takes the children outside once the sun comes out. They finally see the blazing sun and the blue sky. In their astonishment and joy, they all forget about Margot. They run and play in the warm fresh air until the hour is up.

A girl is sad because she sees a raindrop in her hand. Once the rain begins again, the children go back inside. Suddenly, one of the children remembers Margot, still locked in the closet. They all walk slowly towards the closet, realizing what they have done, and let Margot out.

A short film version was made for television in 1982, featuring an expanded ending in which the children atone by giving Margot all the flowers they picked while the sun was out. In the movie she has one friend and never was emotionally distraught.

In this short story it is shown how Margot's individuality makes her peers jealous. However, they eventually feel guilty when they realize what they did was wrong. This story can also teach its readers about the bad qualities of discrimination by seeing the unfair way Margot was treated. In the film version, Margot eventually makes up with William, who was her only friend before the sun came out, after he gives her his flowers. The flowers were givien as a meaning of apology.