Two teenage girls, Sam Kwan and Allie Thompson, find a weather machine at a shack in the woods. After learning of its controls, they use it to make it snow in Los Angeles. The snow is fun for everybody who it affected.
It turns out that the weather machine belongs to Santa Claus who informs Mrs. Claus about this. To help him, she sends Crumpet and Sparky, two elves who look nothing like the traditional design (in other words, as one of them mentions, they are "not 3 feet tall and have squeaky voices").
Unfortunately, a boring weather man named Edwin Hadley tries to figure out what's causing the strange weather and track it down to keep himself from getting fired by his boss, Mr. Martino. Mr. Martino expects him to not act all boring and get down to the bottom of the sudden snow appearances.
When Sparky and Crumpet catch up to Santa at this shack, they find a clue being a footprint of a type of girl shoes that are only made in California. They set off to interrogate each girl on the naughty list that wears those type of shoes.
Soon, the snowstorm gets so large that it spreads to San Francisco and Allie's dad gets snowed in at the airport and may not make it home in time for Christmas. She tries to turn it off, but overnight it turns itself back on and creates a blizzard. They are unable to make it do anything now. Sam shares sad stories with Allie about how her dad would spend Christmas, while Allie is sad about hers missing it.
During the blizzard, Mr. Martino tells Edwin to handle the story about the cast of Friends not being able to leave their studio. He manages to trace the weather phenomenon to Allie's house. Due to traffic, he manages to borrow somebody's snowmobile.
When Sam and Allie head to the shed to get the flashlights, they encounter Santa, Crumpet, and Sparky who identify Allie as the next person on their naughty list. They managed to get proof that he's Santa when he tells them all about themselves and the weather machine.
Edwin arrives at Allie's house and manages to gain entry. He manages to find the weather machine after Allie's brother found it and berated him for messing with it. Upon being cornered in Allie's room by the girls, Santa, Crumpet, and Sparky, he announces his plans to be the best weather man in history and fain more publicity on television attempts. During his escape, he sees the guy he borrowed the snowmobile from and crashes into a chocolate making factory where he falls into a vat. They follow his trail into the factory and follows his chocolatey trail. Sparky follows him up into the rafters where he fall into a box of cotton candy. They then reclaim the weather machine.
At Santa's shack, he then works to find the problem in the weather machine. With Sam and Allie's help, they manage to fix it (Santa forgot to put in the right batteries) and stop the weather. Santa then tells Edwin that there is another type of job that deals with weather.
Crumpet and Sparky pick up Allie's dad just in time for Christmas morning. Meanwhile, Edwin gets a job in the Arctic teaching scientists about the weather.
- Hallee Hirsh as Allie Thompson
- Brenda Song as Sam Kwan
- Hallie Todd as Michelle Thompson
- Spencer Breslin as Joey Thompson
- Greg Kean as Steve Thompson
- John B. Lowe as Santa Claus
- Susan Ruttan as Mrs. Claus
- John Salley as Crumpet
- Bill Fagerbakke as Sparky
- Peter Scolari as Edwin Hadley
- Jason Schombing as Mr. Martino
- Tiffany Desrosiers as Tina