The movie begins with a whimsical discussion on how snow forms, emphasizing that a snow day is not merely a school closure, but a magical occasion. We are introduced to Tom Brandston, portrayed by Chevy Chase, a local weatherman who is reluctantly forced to don a Hawaiian shirt to promote an upcoming warm front. Frustration brews as Tom is stuck in a job that relies on gimmicky stunts to boost the station's dismal ratings.
In the midst of this, we meet Tom's daughter Natalie (played by Zena Grey), who anxiously wishes for a snowfall amidst an oddly warm winter. Natalie and her friends, Chet (Jade Yorker) and Wayne (Josh Peck), resort to using old snowballs to pelt their overly serious principal, Weaver (Damian Young), who unwittingly becomes their prime target. Meanwhile, Tom's son Hal (Mark Webber) pines after his crush, the popular Claire (Emmanuelle Chriqui), while sitting poolside with his friends Lane (Schuyler Fisk) and Bill (J. Adam Brown). During a moment at the pool, Hal nervously fumbles and retrieves Claire's lost whale charm bracelet, intending to return it after learning of her breakup with her jock boyfriend, Chuck (David Paetkau).
At a family dinner, as Tom’s workaholic wife, Laura (Jean Smart), finally arrives at home, the kids, including lively Randy (Connor Matheus), briefly rehearse their grievances while awaiting her. The atmosphere shifts when Natalie shakes a snow globe, wishing it would summon snow. Just as Tom preps for a sunshine forecast, he suddenly detects a snowstorm on the radar, leading to a delightful surprise the following morning: a winter wonderland with schools officially closed.
Fueled by excitement, Natalie dreams of using the snow day's enchantment to defeat her arch-nemesis, the nefarious Snowplowman (Chris Elliott), infamous for plowing the streets too efficiently, ensuring no snow day in years. Natalie recruits Hal’s assistance, but Hal is preoccupied with his crush on Claire, hoping to seize the snowy day to return her bracelet and profess his feelings.
Laura's plans to get to work inevitably fall through as she gets snowed in at home with Randy, while Principal Weaver grapples with relentless snowball attacks. As the story unfolds, Lane warns Hal about the perils of love, advising that lasting relationships are borne from genuine compatibility, not fleeting attraction.
As Natalie and her friends construct an igloo fort, their showdown with the Snowplowman begins, leading to slapstick chaos when he maliciously destroys their creation. Hal's quest to declare his feelings for Claire takes unexpected turns, including a live TV spectacle at the weather station.
Amidst hijinks involving Natalie’s clever pranks and Hal’s misadventures at the skating rink, the film weaves a heartfelt narrative about sibling antics, childhood romance, and the jubilant spirit of snowy days. The climax comes as Natalie rallies an army of kids to confront the Snowplowman, culminating in a hilarious showdown.
As the day winds down, the characters reflect on their respective journeys, highlighting Hal’s evolving feelings towards Lane and his making amends. The film closes with a humorous twist involving Principal Weaver, showcasing just how magical—yet chaotic—a snow day can truly be.
