On an expedition in Antarctica, paleoclimatologist Jack Hall and his colleagues Frank and Jason are drilling for ice-core samples on the Larsen Ice Shelf for the NOAA when the shelf breaks off.
Later, Jack presents his findings on global warming at a United Nations conference, but fails to convince diplomats or Vice President of the United States Raymond Becker. However, Professor Terry Rapson of the Hedland Climate Research Centre in Scotland believes in Jack's theories. Several buoys in the North Atlantic simultaneously show a massive drop in the ocean temperature, and Rapson concludes that melting polar ice has started to disrupt the North Atlantic current. He contacts Jack, whose paleoclimatological weather model shows how climate changes caused the first Ice Age. His team, along with NASA's meteorologist Janet Tokada, builds a forecast model.
Across the world, violent weather causes mass destruction. U.S. President Blake authorizes the FAA to suspend all air traffic due to severe turbulence. At the International Space Station (ISS) three astronauts see a huge storm system spanning the northern hemisphere, delaying their return home. The situation worsens when the storm system develops into three massive hurricane-like super storms with eyes holding -150 degree temperatures that freezes anything it comes in contact with.
The weather becomes increasingly violent, causing traffic-jammed Manhattan streets to become flooded knee-deep. Jack's son Sam, visiting New York City as he is participating in a decathlon, calls his father, promising to be on the next train home, but flooding closes the subways and Grand Central Terminal. As the storm worsens, a massive storm surge hits Manhattan. Sam and his friends seek shelter with a large group of people in the New York Public Library, but not before his friend and love interest, Laura gets injured.
President Blake orders the evacuation of the southern states of the United States, causing almost all of the refugees to head to Mexico. Jack and his team set out for Manhattan to find his son. Their truck crashes into another vehicle just past Philadelphia, so the group continues on snowshoes.