Other mistake: During the garage scene, we see a large neon sign get ripped off of its mounting pole and thrown into the garage. It seems obvious that the sign is no longer connected to any sort of electricity source, however, the sign stays lit as it is ripped off its pole, into the next shot when it crashes into the garage, and then it continues to flicker a bit as it lays on the ground.
Other mistake: The first time we see the NSSL; the woman's name there is Chris. Later in the movie, when we see the NSSL again, her name is Bryce. Turn the captions on so you can tell.
Other mistake: In the scene in the garage pit, one of the characters is hit in the forehead by a flying hubcap. He is cut clear across his forehead, but there is only a small trickle of blood oozing from the wound. I've seen many scalp lacerations and even the most minor ones will bleed like a stuck pig, where's all of that blood?
Other mistake: When the twister hits the drive in theater, the sirens are wailing, but nobody reacts. Only when Jo screams at the waitresses they start panicking and run. The movie is set in Oklahoma, smack in the middle of tornado alley. The people there know what the sirens mean, they sure don't need no out-of-town big-shots to tell them to get under cover.
Other mistake: When Bill and Jo are strapped to the water pipes in the final twister scene, after the tornado passes and they are back on the ground, one of their leather straps are already broken. In this condition it never would have held itself on that pipe, let alone an average sized human being.
Other mistake: When the Tree gets blown under the red truck and they get stuck on it. Why don't they ever put the truck in 4WD? You can see the front differential and 4x4 markings so the truck definately HAS 4WD. That particular year of truck doesn't even require you to get out and lock the hubs.
Other mistake: The order of action performed to activate Dorothy 2 (jumping tornado scene) and 4 (F5 tornado scene) is reversed. Also, Bill somehow has more switches to flip. Jo pressed a button, flipped a couple switches and then told Bill Dorothy was ready, while Bill had to flip the same switches, then flip some more, then press the buttons before starting to unstrap the device from the truck. (Jo didn't have to unstrap D4 because they realised at that point it had to be anchored to something heavy because the device was too light and decided to sacrifice the truck). However it is possible that Bill actually flipped the same switches twice. We can see him flip the switches, then we have a quick close shot of Dorothy 2 then the camera goes back to Bill flipping the switches again. There is no such angle change during the part where Jo activate D4, so it's very much probable that they got two angles of Bill Paxton flipping the switches, but forgot to cut one. (00:59:15 - 01:36:00)
Other mistake: During the movie, some characters wear a headset to communicate (Rabbit, Joey, Dusty, Jo, Jonas). Nothing wrong there, but they also use the CB radio/mic in addition to using the headset. And it's not so they can hear conversations better, since Rabbit and Jonas use the mic on their headsets 99% of the time. There are also instances where you can hear conversations from some of these characters when they don't use the CB radio, so the only mic that makes sense is from the headset.
Other mistake: How come it's the sunniest day ever a few feet from an F5 tornado?
Other mistake: Near the end after Bill and Jo have jumped out of the truck, their crew sees the truck and Dorothy go up in the tornado, they are receiving telemetry, then one of them notices the tornado shift direction and the crew still tries to notify Bill and Jo by radio, knowing they're no longer in the truck nor have radio communications.