The children have never seen snow before. When Scout wakes up that morning, she thinks that the world is ending. School is closed and Atticus allows the children to go out and play in the snow. Jem keeps telling Scout not to walk around in it because it is disappearing, and she is using it up. They are having a wonderful time.
Just then, Mr. Avery, one of their neighbors walks up to them and says,
"See what you've done? ....Hasn't snowed in Maycomb since Appomattox. It's bad children like you makes the seasons change." (pg 65)
Somehow Mr. Avery thinks that bad children cause bad weather. Scout is having such a good time that she thinks if this is what she gets for being bad, she should be bad more often. There is something to be said for being bad or "for sin". (pg 65)
First of all, the "sin" that Scout thinks might apply to Mr. Avery calling them "bad children" is when they watched him urinate off of the porch one evening. That's why Scout says, "I wondered if Mr. Avery knew how hopefully we had watched last summer for him to repeat his performance. . ." (65). Scout thinks that catching him urinating off of the porch was shocking, hilarious, and entertaining. If sin is just as entertaining, then she wouldn't mind seeing something like that again, or possibly dabbling in something else. In addition, if the reward for such an entertaining sin is snow, then she would gladly do it again. The snow is such a wonderful thing to Scout because she had never experienced it before. In fact, she first thinks that snow burns and it takes Jem to tell her that it's so cold that it just feels that way. They also have a fun day gathering up as much snow as they can to build a snowman, which is also a great reward to a child.