A pair of siblings make the most of a school snow day, while trying to avoid their nemesis, the Snowplowman.

When an entire town in upstate New York is closed down by an unexpected snowfall, a "snow day" begins when a group of elementary school kids, led by Natalie Brandston, try to ensure that the schools stay closed by stopping a mechanical snowplow driver by trying to hijack his plow truck. Meanwhile, Natalie's big brother Hal is using this day to try to win the affections of Claire Bonner, the most popular girl in his high school, while Hal and Natalie's father Tom, a TV meteorologist, faces off against a rival meteorologist for weather coverage of the day's events.

When 13-year-old Allie Thompson and her best friend Sam happen upon a weather-making machine discarded by none other than Santa Claus, they use it to cause a snow day in Los Angeles. But when the machine gets out of hand, it threatens to ruin Christmas.