Five years after Astro-X’s breakthrough energy system halted sharknadoes, the company’s founder Aston Reynolds Tommy Davidson unveils a celebratory milestone: the grand opening of a shark-themed hotel in Las Vegas, powered by their sleek Astro-Pods. Fin Shepard Ian Ziering has relocated to a quiet Kansas farm called “April’s Acres” with his mother Raye and his young son Gil, while his cousin Gemini Masiela Lusha accompanies him to the neon-lit city to meet his son Matt Cody Linley, who has just returned from deployment in Iraq. Matt and his fiancée, Gabrielle Imani Hakim, celebrate their wedding in a skydiving ceremony; a dangerous sandstorm forms and, unable to be neutralized by Astro-X, it drains water and sharks from a massive tank inside Reynolds’ Las Vegas hotel, generating a citywide sharknado that floods the streets.
The scene shifts to Astro-X’s high-tech labs, where Colonel Gilbert Shepard David Hasselhoff oversees a weaponized mech suit project with his granddaughter Claudia Ryan Whitney and lead scientist Wilford Wexler Gary Busey. Fin and his family remain unaware that Wilford has secretly rebuilt his daughter and Fin’s wife, April Wexler Tara Reid, as a cyborg to save her life after a previous catastrophe, and he falsely claims that her family was killed in the storm to shield them from harm. Inside the Astro-X facility, Holden Alexandra Paul watches the drama unfold from the control room as the group boards a train back toward Kansas, but the Las Vegas sharknado stubbornly follows, chasing them across the desert.
Arriving at a hidden Astro-X facility, Fin’s group confronts Reynolds, who tries to win him over in a bid to salvage Astro-X’s public image after the hotel’s failure. Back home, April escapes Wilford’s lab and learns of his deceit. A series of new storms — a “lavanado” in Yellowstone, a “hailnado” over San Francisco — begin to ripple across the map, and April shows up to reveal she’s alive, inflaming the group with anger over the deception and the danger.
The team heads to Fin’s farm, where an approaching sharknado forces Raye and Gil into a bunker. The storm shockwaves carry the farmhouse to Chicago, while Reynolds upgrades the Astro-Pods with new isotopes to quell the lavanado and hailnado. Reynolds pilots a plan to fly Shepard, Claudia, and April to Finn’s location, while the rest of the crew contends with a growing crisis. When the nukenado forms after the Perry Nuclear Power Plant in Ohio is hit by the storm’s energy, Reynolds realizes the only way to defuse it is to turn it back into a regular sharknado so the Astro-Pods can work. He proposes using the mech suit’s engines to power a device that will draw water away and cool the storm, with Niagara Falls as the only feasible water source.
As the device powers up, Reynolds sacrifices himself by leaping from a jet in a squirrel suit. The attempt falls short, and Reynolds plummets into the water. Shepard volunteers to pilot the mecha, but he and Claudia and Matt are swallowed by sharks. Fin climbs into the suit himself, reaches the device, and powers it enough to reverse the Falls’ flow and neutralize the radiation, turning the nukenado into a normal sharknado. The Astro-Pods spring to life and wipe out the storm, but Fin is swallowed by a shark that itself is swallowed by three more sharks — followed by a blue whale. Gil hacks the whale open with a chainsaw, revealing that Shepard, Claudia, and Matt survived.
They pull Fin from the animal’s gut and revive him using April’s power supply and two sharks as an improvised defibrillator. In a final surreal twist, the Eiffel Tower plummets from the sky, and Nova — previously hinted as vacationing in Paris — emerges, signaling that the sharknado threat may be spreading globally.
