Une comète doit très prochainement passer près de la Terre. Les calculs savants des scientifiques indiquent que l'astéroïde ne devrait pas entrer en collision avec la planète bleue. Elle ne fera que la frôler, causant quelques interférences magnétiques. Mais un astrophysicien, le Dr James Mayfield, chargé d'étudier ces perturbations, en vient à penser que la comète pourrait tout de même s'écraser sur la Terre. C'est alors qu'un fragment se détache et tombe sur l'Alaska...
A local field researcher named Marshall Clarke (Simon Bossell) is investigating the disappearance of local wildlife, and finds slimy residue on a fence post. Meanwhile, a woman named Amy Harding (Pamela Gidley) moves into her old cabin in the woods of Langdon, where she spent her family holidays as a child, along with her cat, Frankie, and two goldfishes. In the morning, Amy cleans, and fixes up her cabin. She goes to eat some cake, and discovers that something has been in it. Outside, she meets Mr. Peterson (Norman Forsey), looking for his dog Florence, which was killed by an unseen creature, he tells her to get out of Langdon.
While Dori Thorell (Sharon Lawrence) and her 9-year-old son, Danny (Michal Suchánek), eat breakfast, Sam Thorell (Garwin Sanford) calls from his business trip. Ballerina Diane Agostini (Jennifer Garner) is on the phone with her father when a blender shakes off the counter. Dismissing it, she ends the call and rushes off to a rehearsal session at the New York City Ballet. But she's scolded for being late. Public defender Evie Lincoln (Lisa Nicole Carson) talks with her client Joshua Bingham (JR Bourne) about his case. That evening, tremors cause a gas leak at Diane's apartment complex. Though the electricity is still on in the evacuated building, Fire Chief Thomas Ahearn (Tom Skerritt) sends his crew inside. The building explodes, killing several men. At a party at Gracie Mansion, Evie's grandmother Emily Lincoln (Cicely Tyson) chastises her for being late. Her father, Mayor Bruce Lincoln (Charles S. Dutton), coerces her into going to a job interview at a big law firm.
Markey, capitaine dans l'armée américaine, est envoyé en Serbie pour arrêter un criminel de guerre, Dragutin. Au même moment, la présidente Rowntree s'envole à bord de l'avion présidentiel Air Force One avec une jeune journaliste, Romero. Mais l'avion est piégé et doit atterrir d'urgence en Serbie, où se trouve le bras droit de Dragutin, un certain Petrovic. Markey ignore que Petrovic est en fait un agent britannique du MI5…
Kevin Harrison (Robert Wagner), a corrupt arms dealer, attempts to destroy an American-owned Concorde on its maiden flight after one of the passengers, reporter Maggie Whelan (Susan Blakely), learns of his weapons sales to communist countries during the Cold War.
During a routine flight to Minneapolis, a passenger (Susan Dey) aboard Global Airways Flight 502, a Boeing 707, discovers a bomb threat written on the mirror of one of the first-class bathrooms. A second threat is soon found left on a napkin in a galley. Captain Hank O'Hara (Charlton Heston) takes the cryptic threats seriously and follows the instructions -- "Bomb on plane divert to Anchorage Alaska. No Joke, No Tricks. Death"—by changing course for Alaska. To avoid an explosive decompression if a bomb goes off, he flies at lower altitude, increasing fuel consumption.
On July 20, 1969, astronaut Jim Lovell hosts a party, where guests watch on television as Neil Armstrong takes his first steps on the Moon during Apollo 11. After the party, Lovell, who had orbited the Moon on Apollo 8, tells his wife Marilyn that he intends to walk on the Moon's surface.
Markus Voss est le chef de projet d'un gigantesque tunnel en construction. Comme tous les jours, son fils, un adolescent de 14 ans, emprunte la ligne de bus 152 afin de se rendre en ville. A la suite de pluies diluviennes, la route s'effondre brusquement, précipitant le bus dans un magma de terre, d'eau et de boue.
Jay Baruchel arrives in Los Angeles to visit with old friend and fellow actor Seth Rogen, who invites him to attend a housewarming party hosted by James Franco. Jay is uncomfortable being around so many people he hardly knows, so Seth accompanies him to a convenience store for cigarettes.
A park ranger must lead a US senator, a disgraced cop, his wife, a manipulative professor and his daughter across five miles of dangerous terrain to escape an unstable cavern, unaware that the seventh member of the group is an armed and violent escaped convict.
Andy Goodman (Brian Dennehy) is a week away from a forced retirement from his position as chief meteorologist at the National Weather Administration's Severe Weather Center. However, tornadoes level Las Vegas, an area normally not prone to the storms. Concerned and upset that the storm system formed unnoticed and that they were unable to warn the people, Goodman begins closely tracking the system. Goodman receives field reports from his friend "Tornado Tommy" (Randy Quaid) and assistance from new intern Sabrina Rogers (Alicia Johnston). As time passes, he realizes the system is heading towards Chicago, joined by an unusual warm storm coming from the south, which is already causing a record-breaking heat wave in the city, and an abnormally early cold front from the Arctic.
In Upstate New York, a waste management firm loads barrels of toxic waste onto trucks, intending to illegally dispose of them. They are shown heading into a tunnel under the Hudson River between Lower Manhattan and Jersey City, New Jersey along with several other commuters, including struggling playwright Maddy Thompson (Amy Brenneman), some young offenders, a vacationing family, an elderly couple, and a mountain climber named Roy Nord (Viggo Mortensen). Meanwhile, a gang of diamond thieves in a stolen car try to escape the NYPD by racing into the tunnel. The gang force their way through the north tube traffic, spilling the diamonds all over the floor of the car. While a female thief tries to retrieve them, she pushes the gas pedal to the floor, causing the driver to lose control, smashing though a security booth and into one of the trucks, killing them instantly. The waste barrels explode, causing the other trucks to explode and setting off a chain reaction. The tunnel entrances cave in, and a devastating fireball sweeps through the tunnel, incinerating thousands of cars and people.
On May 10, 1998, teenage amateur astronomer Leo Biederman discovers an unusual object near the stars Mizar and Alcor at a star party in Richmond, Virginia with his school's astronomy club. His teacher alerts astronomer Dr. Marcus Wolf, who realizes that the object is a comet on a collision course with Earth. Wolf dies in a car accident before he can alert the world.
Après plusieurs semaines de pluie torentielle, les habitants soucieux de la sécurité de la petite ville de Brownsville demandent à leur maire d'ouvrir les vannes pour faire sortir le surplus d'eau du barrage mais ce dernier refuse. La construction cède et c'est la panique pour les quelques habitants qui vont devoir faire l'impossible pour survivre.