A freak cyclone hits Los Angeles, causing water spouts that scoop up man-eating sharks and flood the city with shark-infested seawater. Bar owner and surfer Fin sets out with his friends, Baz, Nova, and George, to rescue his estranged wife, April, and their teenage daughter, Claudia, after the bar and boardwalk are destroyed by the flooding. While heading to April's home, the group stops in a freeway to save people as flooding causes sharks to attack. George is killed and the group learns of a tornado warning. They arrive at April's house just before the first floor is flooded and shark-infested. Collin, April's boyfriend, is eaten by sharks, but the rest of the group escapes unharmed.
Fin stops the car to save the children stuck in the bus from the assaulting sharks. Afterwards, the bus driver is killed by the "H" in the Hollywood Sign. While Nova is driving the car, a shark lands on top of the car and rips the roof off. Fin's hand is cut and the group abandons the car before it explodes. They steal another car and meet up with Fin and April's son Matt, who is found taking shelter at his flight school. They borrow equipment from a nearby storage and Matt and Nova become attracted to each other. Matt and Nova decide to stop the threat of the incoming "sharknadoes" by tossing bombs into them from a helicopter. Two are destroyed, but they are unable to stop the third one.
As Nova fights off a shark that had latched onto the helicopter, she falls out of the helicopter and directly into another shark's mouth. Matt is heartbroken. Baz is also lost in the storm along with Matt's friends Bobby and Luellyn. Ultimately, Fin destroys the last sharknado with a bomb attached to his car and the sharks begin to plummet toward the ground. One falling shark flies directly toward the remaining members of the group. Fin jumps into its mouth with a chainsaw and cuts his way out. He emerges carrying an unconscious but otherwise unharmed Nova. Matt is reunited with Nova, and Fin gets back together with April.Ian Ziering as Finley "Fin" Shepard, an ex-surfer who owns a bar.
Tara Reid as April Wexler, Fin's ex-wife.
John Heard as George, a drunk man who spends all his time at Fin's bar.
Cassie Scerbo as Nova Clarke, a bartender who works for Fin.
Jaason Simmons as Baz, Fin's right-hand man.
Aubrey Peeples as Claudia Shepard, April and Fin's daughter who feels left out.
Chuck Hittinger as Matt Shepard, Fin and April's son in flight school.
Christopher Wolfe as Collin, April's boyfriend.
Robbie Rist as Robbie, a bus driver.
Alex Arleo as Bobby, one of Matt's friends in flight school.
Connor Weil as Luellyn, one of Matt's friends in flight school.
Julie McCullough as Jonni Waves, a news reporter.
Adrian Bustamante as Kelso, a lifeguard.
Sharknado was directed for film studio The Asylum by Anthony C. Ferrante, whose previous directing credits include the horror film Boo, and written by Thunder Levin, whose previous writing credits include the film Mutant Vampire Zombies from the 'Hood!. The film's tagline is "Enough said!" Sharknado is one of many B-movies commissioned by Syfy. Robbie Rist said in an interview that he came upon the film's poster at the American Film Market and became enthusiastic about the concept. When his friend Ferrante said that he had been approached to direct the film, Rist insisted that Ferrante take the job. Rist was given a small role in the film and composed the theme.
Actress Tara Reid said of the film, "It is silly, and there's only a certain amount of barriers you could go into. You can't take it so seriously when it's absolutely the sharks flying in the sky. It's so out there that it's actually really funny." The cast had to imagine the presence of sharks due to a green screen being frequently in use. Ian Ziering stated that he had serious reservations about the script but was motivated, in part, by the need to earn enough to qualify for Screen Actors Guild health insurance for his family.
In an interview with Uproxx's Danger Guerrero, Ferrante summarized the film's plot: "There's a flood. And a storm. Don't worry about it."
The premiere of the film was watched by 1.37 million viewers, which is slightly below the average audience of 1.5 million viewers for a typical Syfy original film. The film was a trend on Twitter, including discussion by celebrities such as Damon Lindelof, Wil Wheaton, and Olivia Wilde and also by Cory Monteith, whose last tweet before his death was about the film. Due to an increase in publicity (mostly through Twitter), Syfy repeated Sharknado on Thursday, July 18, 2013, one week after its premiere. The airing was watched by 1.89 million viewers, an increase of 38% over its initial airing. On July 27, a third airing of Sharknado got 2.1 million viewers, continuing the increase in popularity of the film and setting a record for most watched original film encore in Syfy history. Sharknado is projected to increase revenue for The Asylum from $5 million in 2009 to $19 million in 2013.
A representative of the National Weather Service jokingly recommended what to do in case of a sharknado, saying: "As with any waterspout or tornado, the best advice is to be in an interior part of the lowest floor of a sturdy building – and not outside, whether sharks are raining down or not." Organizations such as the Red Cross of Oklahoma City also used the film as an opportunity to pass on storm safety information while others incorporated it into their own advertising.
Regal Cinemas announced that at midnight on August 2, 2013, it would play the film in roughly 200 theaters nationally. Tickets sold out quickly in New York, Boston, and Seattle, where more showings were added to appease customer demand. Box office numbers were weak for the midnight showings; estimates were at under $200,000.Australia – Premiere on the Universal Channel was scheduled for September 9, 2013, but was fast-tracked to premiere on July 26, 2013, after the film's wide international response. It rated 54,000 viewers, making it the sixth most watched program for the night (and third most watched non-sport program) on subscription television.
United Kingdom – Premiered on Syfy on August 7, 2013.
New Zealand – Premiered on free-to-air television channel Prime on September 17, 2013.
Germany – Premiered on free-to-air Tele 5 television channel on January 10, 2014 as part of their "Worst films of all times" series.
Syfy and The Asylum announced in August 2013 that Sharknado merchandise would be made available, including T-shirts and potentially other products. Funko acquired the licensing agreement to manufacture the POP Vinyl version of Sharknado
Rotten Tomatoes gives the film an approval rating of 82% based on 17 reviews; the average rating is 6.1/10. The site's consensus states: "Proudly, shamelessly, and gloriously brainless, Sharknado redefines 'so bad it's good' for a new generation."
Reviewer Mary McNamara, writing for the Los Angeles Times, mentioned that the plot holes are "the whole point of movies like this: fabulous in-home commentary. Often accompanied by the consumption of many alcoholic beverages." David Hinckley of the New York Daily News said "Sharknado is an hour and a half of your life that you'll never get back. And you won't want to."
Kim Newman of Empire called the film "cynical rubbish, with an attention-getting title and just enough footage of terrible CG sharks in a terrible CG tornado chomping on people to fill out a trailer suitable for attracting YouTube hits."
Sharknado has become a cult film. The film was used for a RiffTrax Live event in July 2014, where former Mystery Science Theater 3000 cast members mocked the film for a live audience and broadcast to other theaters through NCM Fathom; the idea for using the film for this was prompted by the Sharknado producers discussing the film with Fathom at the same time. After the event, Ferrante said that "Being skewered by the MST3K guys was an honor." In 2016, Homes.com added a page to their disaster prep guides on How to Prepare Your Home For a Sharknado.
The success of Sharknado spawned a series of sequels with the fifth entry in the series announced in early 2017.