In the first scene at the end of the bike race, Dan has an earring - until he and Arthur go for a ride. From then on, it is missing.
When Dan puts Ryan to bed, the baby is dressed in regular clothes. When the tornados start and Dan goes to get the baby from his crib, Ryan now has on blue pajamas.
In the scene where the tornado approaches the house and Dan tries to get Ryan from his collapsed crib, the wind pushes Dan to the window. The tornado is seen approaching from the window, but there are no homes or trees on the ground even though trees are shown to be located surrounding the house in an earlier establishing shot when Dan and Arthur ride their bikes to Dan's house.
In the scene in which Dan, Ryan, Jack, Laura, Bob, and Jenny are trying to outrun the twin tornadoes in their cars, the station wagon Dan, Ryan, Jack and Laura are in drives past a house which immediately explodes as the tornado approaches it. Seconds later, the truck passes by the same house and the scene is shown again but at a different camera angle.
Just before the tornado hits Dan's house, two scenes showing the shingles on the roof lifting up also show the rain falling vertically. Winds strong enough to cause the roof tiles to lift up would violently blow the rain almost horizontally.
The tornadoes can't seem to lift up heavy vehicles including firetrucks or school buses.
The twisters in this film seem to be all gray. They were supposed to be black.
When the kids are retrieving their bikes from the rain storm, you can see a brighter, studio lighting effects to make up the lightning portion, there when they flash the lights to light up the side of the house, Lightning does not light up a full side of the house, or light up the same side of the house multiple times in the same way.
When the meteorologist tells everyone to outrun the tornadoes in the cars, he is contradicting his previous statement (as well as real-life tornado experts) that cars were not a safe place to be during a tornado. However, he states that "There's really no place around here to take shelter" indicating that the cars are their only option.
When the family is "escaping" from the twin tornadoes toward the end of the movie, the trash can that flies onto the windshield has almost no momentum and it flies in a slight upward arc before lightly hitting the glass; it was clearly tossed from just off screen.
During the tornado scene at Dan's house, a table spins in the basement, which is impossible.
When Dan and the rest are in the basement of his house while is being struck by the tornado, there is silence. There a chair moves being being caused by the wind, but nothing else moves.
When the tornado is wrecking Dan's house. There is a scene where water is sucked through the toilet and the very next scene shows it shooting out of the stink pipe. This is impossible. When water gets flushed down the toilet, it goes through a different pipe in the floor. The stink pipe is connected to the fan(s) on the bathroom ceiling.
The siren sound effects in movies are Carters sirens from the UK, recorded during WWII, not modern American emergency sirens.
In several scenes, Ryan can be heard crying, although he is not actually seen doing it.
When the kids are retrieving their bikes from the rain storm, you can see a brighter, studio lighting effects to make up the lightning portion, there when they flash the lights to light up the side of the house, you can make out a shadow figure on the right side that is a human-like figure.
When Dan is retrieving Ryan from the bedroom during the tornado scene, Dan is being "sucked to the window" by the winds, you can see a brighter, studio lighting effects to make up the lightning portion, there when they flash the lights to light up the side of the house, you can see a shadow figure of a crew member.
About 6:25 seconds in, you'll see speed limit signs on the side of the road that is says "MAXIMUM 40" which indicates this was filmed in Canada and not the United States, because United States has "SPEED LIMIT 25 MPH".
In Nebraska, there is no town named Blainsworth, though there is an Ainsworth that would be similar in size to the town portrayed in the movie. However, Ainsworth is over 130 miles NNW of Grand Island, Nebraska, where the tornado outbreak actually took place. Grand Island would've had a population of 35,000 or so in 1980, which is considerably larger than fictional Blainsworth's population.
The characters shelter in a firetruck, a notably poor place for cover from a tornado.
When giving his weather briefing in the Community Center, Bob references that one of the storms that touched down are at least a 5 on the Fujita scale. However, 5 is the highest the Fujita scale measures.
Near the end of the film when the Hatches, Jenny and Bob outrun the tornado in their vehicles, they all park under an overpass for shelter. However while only Bob and Jenny exit their vehicle and the Hatches remain in their station wagon, weather experts have noted that it is extremely dangerous to take shelter under overpasses due to the Bernoulli effect, increasing the tornado danger by increasing wind speeds and funneling debris under the overpass.