Factual error: The kids are leaving a movie theater that's playing I Was a Teenage Werewolf. This film was released in June of 1957. So one, they are in 1960 and this film would not still be playing. And two, they were shown still attending school, but they would not be attending school in June during summer break.
Factual error: During the scene while Georgie is running with his boat, look at the grass, and you can see that there is a good amount of sunlight. This wouldn't make sense to have a lot of sunlight during a big rainstorm. It should have been darker due the shadow of the thunderclouds.