Filmed in Kleinburg, Ontario, Canada and based loosely on the 1984 young-adult novel of the same title by Ivy Ruckman (a semi-fictionalized account of an outbreak of seven tornadoes that struck Grand Island, Nebraska on June 3, 1980, killing five people and injuring 134 others), the film centers on a family's struggle to survive a night as a bizarre tornado-producing supercell thunderstorm tracks into and becomes stationary over their town.
The film's prologue takes places in an area of rural farmland in Dannebrog, Nebraska in Fall 1996. While there, Bob Irisen – a storm chaser with the National Weather Service – is driving down a country road to track a massive supercell thunderstorm. As a tornado touches down yards away, right as their daughter Sarah, arrives home from school, Bob warns a family living nearby, about the oncoming twister, which sends them running into their root cellar just before it destroys their farm.
Meanwhile, in (the fictional town of) Blainsworth, Nebraska (the book is set in the real-world city of Grand Island, Nebraska), teenager Dan Hatch, an aspiring and practicing artist who is constantly being pushed by his stepfather Jack to be an athlete, participates in a bike race and damages his bicycle; Jack pushes Danny into finishing the race on his bum bike, where he falls behind the other racers. Much to his luck, he wins a new bike in a raffle held by a local bank. While trying out his new bicycle, Dan and his best friend Arthur Darlington run into Arthur's two sisters, Stacey (whom Dan is infatuated with) and Ronnie Vae, while at the park. Dan and Arthur arrive home as the former's mother Laura is preparing dinner, when she also asks Dan to tend to his baby half-brother, Ryan. Later, Laura's sister, Jenny, calls to inform her that they have been assigned to a fill-in shift as waitresses at the Salty Dawg, the local diner where they both work.
On the road, while continuing to track the massive storm creeping toward the town, Bob decides to head southeast into Blainsworth, as Stan - the meteorologist he is radioing to - is astonished at the rogue uncharacteristic spring-like nature of the storm system for the fall when it is far too cold; while there, he meets Laura and Jenny while getting some coffee at the diner. The action begins after Jack comes home at mid-evening; as he sits down to watch television, the show he is watching is abruptly interrupted by a KHAS-12 severe weather bulletin about a tornado having been reported near Dannebrog, 14 miles (23 km) northwest of Blainsworth. Several minutes after Jack leaves to check on his mother, Belle, who was fast asleep in her rocking chair when he phoned her, tornado sirens suddenly blare throughout town, only to cut off abruptly as Dan goes to get Ryan from his crib. The eerie stillness outside afterward suddenly gives way to a violent tornado that approaches Blainsworth's Capital Heights neighborhood, with the sucking noises emitting from the drains notifying Dan and Arthur of its pending arrival; they and Ryan take cover in the basement bathroom's shower as the twister starts to obliterate the Hatches' home.
After Dan and Arthur escape from the basement of the leveled house through the collapsing floor beams where the first floor once stood, and look in awe of the rubble that was once the Hatch family's home, Arthur runs into Stacey and Ronnie Vae, who both survived the twister themselves in the Darlington's home (their parents were out of town on a trip back home to California at the time the storm hit). As Dan struggles to find his own family, Laura and Jenny are trapped inside the Salty Dawg (as they were taking cover inside, due to Jenny's 1992 Buick Skylark Gran Sport coupe malfunctioning), which also was destroyed by one of the tornadoes. Dan and Stacey then go save Dan's grandmother, Belle, at her farm; the two teenagers find Belle underneath wooden boards blown onto her from off of the partially damaged barn near her house (which itself survived intact).