Plot:
Fin Shepard and his ex-wife April Wexler are flying to New York City to promote How to Survive a Sharknado and Other Unnatural Disasters, a book April has written about the Los Angeles sharknado. As the plane comes in for a landing through a storm, it is battered by airborne sharks, losing an engine. Sharks enter the plane, killing passengers and crew, including both pilots. While Fin successfully lands the plane, April's hand is bitten off by a shark while she attempts to shoot it with an air marshal's handgun.
Fin's sister, Ellen Brody, is sightseeing in New York with her family. Her husband, Martin, a childhood friend of Fin's, takes their son, Vaughn, to a Mets game at Citi Field along with Martin's and Fin's friends Skye (who is also Fin's ex-girlfriend) and Brian. Ellen takes their daughter, Mora, to the Statue of Liberty where she meets with her friends, Polly and Chrissie, who tell her about Fin's flight.
At the airport, Fin warns the crowd of the impending storm, but no one takes it seriously. After accompanying April to the hospital where she undergoes surgery, Fin receives a call from Ellen and tells her to get back from Liberty Island as soon as possible. He agrees to retrieve Martin and Vaugn from the ball game, hiring a cabbie, Ben, to take him there. At Citi Field, Fin first encounters Skye. She kisses him, but he explains that he and April are back together. Fin gets them all to leave with him just as the storm arrives at the park. The sharks kill people as Fin and his group use various improvised weapons and make their way to the subway.
Ellen's group takes the ferry to Manhattan, but a shark jumps onto the deck and kills Chrissie en route. The three remaining women escape into the city but must flee from the Statue of Liberty's severed, rolling head.
The floods, imperiling Fin's group as their train is chased by sharks. Brian is killed, but the others manage to escape onto a platform. Fin calls Ben to pick them up, and they go in search of weapons and explosives. They arm themselves, but the taxi is then caught in a flood. Fin rigs a rope swing that takes Skye, Vaughn, and Martin to safety, but Ben is killed in his attempt. Fin then jumps across the sharks, using them as stepping stones to reach the others.
Two sharknadoes are converging into a more powerful storm directly above the hotel where Fin and April were planning to stay. Arriving at the hotel, Fin and Skye go to the roof to destroy the sharknadoes with their makeshift bombs. Polly is killed when a shark lands on her, but Ellen and Mora successfully reach the hotel, reuniting with Martin and Vaughn. Fin and Skye launch their bombs into the tornadoes, but the storm system is too cold for this to be effective; the bombs only force them to flee downstairs, away from the flaming sharks that are now falling on them. They meet the Brodys, who are fleeing upstairs due to a rising flood of sharks. They break down a door to escape the stairwell and are able to get out of the building.
Meanwhile, April rescues a young girl at the hospital and sets out to find Fin. She arrives at the hotel in a fire truck and takes them all to the Empire State Building where a third tornado is merging with the other two. The mayor is there with a task force, and they welcome Fin's help. He plans to detonate a tank of Freon at the top of the building by connecting it to the structure's lightning rod, freezing the storm. Fin tells a crowd of New Yorkers to prepare to fight the sharks that will fall from the sky after he destroys the tornadoes. He and Skye implement the plan, while April, who has affixed a circular saw to her stump, saves Fin from a shark. They successfully destroy the storm system, but Skye is killed by a shark and ripped in half. Fin retrieves April's hand from a shark's mouth and uses the gun to defend them against the falling sharks. The New Yorkers in the streets also defend themselves successfully. Fin takes the ring from April's severed hand and uses it to propose remarriage, and she accepts.