Michael Crichton and his wife Anne-Marie Martin were paid $2 million for their script.
Shot over a period of 95 days.
The base camp (where the crew trucks and equipment was staged) for the end sequence of the film was at a pig farm down the road from the well-house. Every morning the cast and crew were greeted by the aroma of a 2 acre pig-waste holding pond in the middle of all the trucks.
Both Joss Whedon and Steven Zaillian were brought in as script doctors at a fee of $100,000 a week.
Laura Dern was considered for the role of Dr. Jo Harding.
An urban legend states that a tornado hit a drive-in theater in the town of Stoney Creek, Ontario while this movie was playing. What really happened was that on May 21, 1996 a tornado hit a drive-in theater that was scheduled to play this movie. The movie was not actually playing when the tornado hit.
The 21 August 1995 draft of the screenplay credits Joss Whedon and Jeff Nathanson as writers. Neither are credited in the final film.
Many of the news reports spread throughout the movie are actual weathermen from Oklahoma news stations, including Gary England, chief meteorologist at KWTV in Oklahoma City, and Rick Mitchell, chief meteorologist at KOCO in Oklahoma City. The "1969" footage of Gary England giving the televised tornado warning to Jo's family is actual archived footage of him issuing a tornado warning; however, Gary England did not join KWTV until 1972.
Lois Smith's character is reading Dante Alighieri's Inferno when the twister hits Wakita. The book also features a tornado in the second circle of Hell that punishes people ruled by Lust.
Jan de Bont said he regretted thinking of the hail sequence because it took so long to do and was very difficult. Also the crew couldn't find ice blocks big enough in Oklahoma, so they had to find them in other states.
Right after Bill and Jo come out of the toppled house, the teddy bear that hits their truck is CG.
According to the book on the making of the movie, the CGI cow picked up by the twister sisters was originally a CGI zebra from Jumanji (1995).
During an early scene when Philip Seymour Hoffman is sitting on a lawn chair, he lifts his leg in the air while laughing. His genitals were fully visible for a split second; this was edited out for DVD and VHS releases, but was leaked from VHS screeners sent to industry professionals.
Jan de Bont is a fan of singer Tori Amos, and decided early on he wanted to include some of her music in the film.
The project was a co-production between Universal and Warner Bros. That is why the drive-in marquee shows Psycho (1960) a Universal release and The Shining (1980), a Warner Bros. release.
The red combine used in the film is now in Watrous, Saskatchewan, Canada.
The laptops used in the film are Silicon Graphics Indy Presenter LCD screens (not real laptops) that have been modified to look like functional laptops when in fact the screen image is generated by a computer off-screen.
The instrument package used in the movie, "Dorothy", is actually a homage to the instrument pack real tornado researchers attempt to place in the paths of tornados, "T.O.T.O.".
Was the first movie released on DVD, and the last to be released on HD-DVD.
The original Director of Photography was Don Burgess (best known for his collaborations with Robert Zemeckis), but he and many other crewmembers walked off the set midway through filming after a series of heated arguments with director Jan de Bont.
The real town of Wakita, Oklahoma had part of its old downtown area demolished by the film crew for the scenes after the twister passes. The studio then paid for the downtown to be rebuilt. The town also kept the new fire truck used in the film.
"It sucks" was originally going to be used as one of the taglines for the film, but the producers felt that it worked too much to the advantage of disappointed audiences and critics.
Helen Hunt was injured while filming the scene where the truck drives through the corn, when the door was forced back into her head. For later shots, the door was wedged open.
Trailers contain a shot not in the film: a truck tire hurtling towards the viewer.
A recording of a camel's moan was slowed down and used as the sound of the tornado.
A jet engine from a Boeing 707 was used to generate wind in some scenes.
In order to get the background skies looking suitably stormy, the truck cab sequences had to be flooded with high-intensity lighting for contrast. As a result, Helen Hunt and Bill Paxton suffered minor retinal burns through much of the filming.