Trivia

After the Las Vegas tornadoes, Andy mentions that they were as strong as "Oklahoma City in 1999." Later in the movie when several stock videos of tornadoes are shown as the storm approaches Chicago, the video of the large tornado with the small satellite tornado to the left of it is the actual tornado that hit the Oklahoma City area in 1999. It is often referred to as the Bridge Creek Tornado due to the horrific damage it caused in that community, and at the time and still to this day it had the highest winds recorded in a tornado in history.

The two individuals staring out of the doomed Arch's observation windows are Craig Weiss (Visual Effects Supervisor) and Niel Wray, (Lead 3D Animator) of CBS Digital, one of two companies that created the Visual Effects for Category Six, the second company being Area 51.

The tourists and pedestrians running for their lives as the Arch collapses are all (but one) CBS Digital artists, ranging from Compositors to Animators and Support Staff.

Towards the end of the film, there is stock footage from the television movie, The Great Los Angeles Earthquake (1990)

Brian Dennehey's character's name is Andy Goodman in the movie. Brian Dennehey is a frequent participant/actor/playwright every year at the Goodman theatre in downtown Chicago.