After the bloody scene in the storeroom, David (Thomas Jane)'s shirt is wet but not very soiled. When he steps into the market, there is a large smear of blood on his shirt.
The blood splatter on the windshield goes from being in the middle of the broken glass to being spread out across the windshield and then back again.
Right after the mist covers the market, when Mrs. Carmody says "It's death," the parking lot, cars, and trees are clearly visible in the reflection on the glass in front of her. Preceding and subsequent shots show that the mist has fully concealed the entire lot up to the sidewalk in front of the store.
When David (Thomas Jane) is seen repeatedly beating down on one of the winged creatures in the grocery store with a mop, there is one brief camera shot that clearly shows the end of the mop still attached (it had been removed moments earlier). The next shot shows the mop without the end.
When the group is finally leaving the market, the bright headlights and all the auxiliary lights on the truck would produce a bright, blinding wall of light in the mist. Nothing would be visible in front of the truck.
Strangely enough, the military convoy at the end of the film is led by a self-propelled howitzer, not a tank. This type of vehicle was not meant to be on the front lines but was a support weapon, and thus wasn't suited to lead a convoy into a danger zone. An actual tank, which should have led the line, can be seen in the back as the convoy goes by.
Central Maine Power (CMP) trucks have an orange cargo area with a white cab, unlike those shown in the film.
Jim (William Sadler) refers to Morales (Juan Gabriel Pareja) and Donaldson (Walter Fauntleroy) as "peckerwoods". Morales is Latino. Donaldson is African-American. The dictionary defines "peckerwoods" as Southern U.S. slang for "poor whites".
Mrs. Carmody (Sobre-Natural (2007)) is supposedly a devout Christian, yet refers to the book of "Revelation" as "Revelations". This mistake is quite common even among people who claim to be devout Christians. She is not an ideal model of mental health, either, allowing some leeway in this matter.
The headline "Electric storm largest on record" on The Castle Rock Times is accompanied by "placeholder" text, commonly known in the publishing and design world as "Lorem Ipsum"- a derivative of Latin that is meant to have no meaning. Same for the text underneath the "Celebrating Heritage" blurb above the masthead.
When the tree "falls" through the window of the house at the beginning of the film, it comes straight in. The tree was clearly pushed into the window rather than falling over.
The fallen tree which crashed through the house of David Drayton (Thomas Jane) at the film's beginning appears to have had its roots cut.
As the group walk up to the pharmacy, you can see the business hours on the door glass readable from inside, whereas you should see them backwards (from inside) so that someone walking up to the door would see them correctly. However this is because the doors are propped open and the exterior of the front of the door is being seen through the glass window from inside the store. So the lettering is correct.
After Norm the bag boy (Chris Owen) is killed, the store generator is shut off. Yet when David (Thomas Jane) recounts the incident to the gathered shoppers, the overhead lights are on.
When the emergency services are rushing towards the mist at the start of the film, a fire truck emblazoned with "CADDO PARISH" is visible. Caddo Parish is in Louisiana and Maine has counties, not parishes. Parishes are the term for counties mostly found in Louisiana.
Throughout the movie, but prominently in a scene where David (Thomas Jane) is standing with some shelves behind him, the shelves are stocked with Zapp's potato chips (specifically the orange 'Hotter 'n Hot Jalapeno' flavor). Zapp's are not sold in Maine. Zapp's Potato Chips is a company based out of Gramercy, LA, and they market their products largely across the South. Zapp's ARE sold in Shreveport, LA, where the movie was filmed.
Towards the end of the film, a white-and-yellow state police car, very similar to an Illinois State Police car, is shown turned upside down, but marked Maine State police cars are blue with a round state police logo on the front doors and the words STATE TROOPER on the front of the hood and above the front wheel well.
When the flying insects arrive and the lights need to be doused, several people turn on all the lights instead for no reason.
In the beginning when David goes to speak to his neighbour Andre over the fallen tree Andre calls David 'Ed' when the character is called David.