The story begins in Antarctica. We see a small group of scientists working on the ice. The leader of the scientists is a paleoclimatologist called Jack Hall. He is joined by his colleagues Frank and Jason. They are all drilling in the ice so they can take a few samples. This is very important research and they have been doing it for a while. Suddenly the ice shelf starts to break apart. Everything starts to crumble. Jack sees that all their equipment and dana might get lost but he must make a daring jump. Jack jumps over the newly formed crack in the ice and retrieves the data. He almost falls in but his friend saves him.
After some time passes Jack passionately presents his results to the United Nations. There is a giant conference about global warming and he explains that the results of his research are really worrying. He explains that when this natural disaster starts, humanity will be doomed. While he is very respected in the science community, Jack does not manage to win over the Vice President of the United States. That man is called Raymond Becker and he tells Jack that the economy could get ruined because of his scary research. After the conference Jack meets professor Terry Rapson, he works for the Hedland Climate Research Center and he truly believes that Jack has uncovered something really important.
In the meantime, strange weather occurrences start to happen all over the world. We see a pair of scientists see a major drop in temperature in several locations, something that has never happened before. Rapson is certain that the polar ice caps have started to melt and now the entire earth is in danger. This also happened in the ancient past and it caused the first Ice Age. Rapson and his team at NASA start to build a weather model that might predict what will happen. They are joined in their research by Janet Tokada.
We are then introduced to Jack’s family, his wife and son Sam. Sam has gotten in trouble in school and has flunked a subject. Jack does not spend enough time with his family because he is working all the time. He promises to pick up his son from school and take him to the airport. While at work Jack has a confrontation with his boss who is angry at him. It seems that the vice president Raymond really dislikes Jack and has decided to cut funding to their entire company.
Jack runs late but manages to pick up his son Sam. They talk in the car and Sam reveals that he only failed that subject because he embarrassed his teacher. Sam is actually really smart so he is really bored at school. Jack has a hard time connecting to his son. Sam boards a plane with his friends and they go visit New York. Sam has a fear of flying and the horrible turbulence does not make it any better. While that is happening horrible weather storms have started to happen all over the world. We see a giant hail storm in Asia and many people die in the storm.
Many other countries experience the same thing. Massive destruction all around and people are starting to get scared.
Sam, his friend Brian and Laura all take part in a special competition. They represent their school and it’s very important. Sam is only doing it to spend more time with Laura as she is his crush. After the competition they all hang out in a festive setting. Sam is jealous as Laura is spending time with another student.
While that is happening, giant twisters appear in Los Angeles. The damage is giant and the city gets destroyed. Many people die in the process. We see a reporter get killed in a brutal fashion by the powerful winds. Also many buildings get hit pretty hard and are barely standing. The tornados decimate much of the landscape and then they suddenly stop. Jack realizes that his research was correct but the natural disaster is starting far earlier than he thought.
US president Blake is now afraid and seeks advice from his cabinet. They decide to suspend all air traffic as its just too dangerous. Jack meets up with a bunch of the most brilliant scientists and they all start to analyze the data. Jack informs them that this might have been caused by the melting of the ice caps and he thinks that the situation is only going to get worse. Jack thinks that the Earth is on the brink of a major climate shift. He tries to prove his research but his boss denies him access. He joins forces with other scientists at the facility and they work for 24 hours to find new information. Soon they all realize that these horrible climate events will happen very rapidly, they do not have much time.
We see that the astronauts at the International Space Station are watching the Earth from space. There are huge storms happening all over and they are so big they can be easily seen from space. Sam calls Jack and he promises that he will be out of New York with the first train tomorrow. Sam does not really take the situation seriously, he is only focused on Laura. Laura, Sam, Brian and that annoying other student all spend time together in New York.
In the meantime Jack tries to convince the vice president to order a evacuation on a large scale. The vice president thinks that Jack is crazy and he ignores his warnings. Later the situation on earth worsened a lot. Now there are many massive storms all over the planet. There are actually massive hurricanes that have formed worldwide. In the eye of the storm, the temperatures drop to −150 °F. we see several army helicopters travel in the eye of the storm. Their entire helicopters freeze in mere seconds and they fall to the ground. One of the pilots survives and as soon as he gets out of the helicopter his entire body freezes. It’s revealed that the temperatures are so low that it freezes anything it comes in contact with. The three large hurricanes are located over Canada, Siberia, and Scotland.
Meanwhile the city of New York is hit by a giant storm. There is flooding all over the city. Sam and his friends are now in a giant apartment complex where the rich student lives. They watch the news and realize that the situation is much worse than they originally thought. Suddenly the building loses electricity. Sam realizes that they must hurry back home before its too late. They all pack up their stuff and go outside. The streets are now really flooded and there are massive traffic jams all around the city. Soon Sam and his friends realize that the entire Grand Central Terminal station has been flooded. They now have no way of getting out of the city as the trains are not working. They are now in the middle of Manhattan with no exit and the storm is just getting worse.
Many people in the city are now panicking as the streets are totally covered in water. People find a hiding spot in the New York Public Library. Sam leads his friends to higher ground as the flooding gets worse. We see police officers saving people and taking them out of their cars that are stuck in water. Sam and his friends finally reach the library and hurry inside. Laura by accident gets injured while traveling. She starts to bleed pretty bad and has a hard time moving.
The storm gets so bad that a giant tidal wave is created. This wave is so big that it destroys the statue of Liberty and is going to hit the entire city. People are now running as fast as they can. Sam notices that Laura is not with them. Instead Laura has managed to walk and she is helping a French family get out of their cars. The tidal wave hits the city and we see many people running to safety. The people who are so slow get taken away by the water. Sam runs after Laura and they manage to find shelter in the Library at the last moment. All the streets of New York get swallowed by the giant wave.
Jack gets in contact with Terry and his team in Scotland. They confirm that the storms will only get worse. The new Ice Age will start very soon. Terry and his team are very near the storm and they have no chance of exiting to safety. Terry tells Jack that he now has to save as many lives as he can.
Jack meets with President Blake and a large-scale evacuation is ordered. Many people migrate to Mexico as they can be safe there for a while. Jack also tells the president that the people who did not evacuate need to hide or they will die in seconds. Sam and his friends are now safe with the people inside the library. The entire city is flooded. Sam decides to get into contact with his father. He dives in a flooded area of teh library and calls his father. Jack tells Sam that he must stay inside as soon the entire city will be frozen. Jack goes with some of his coworkers to New York to save his son. The weather changes once more and everything starts to freeze and a snow storm hits the world. Jack and his crew crash their truck and they must walk the rest of the way in snow.
After it starts to snow the people in the library decide that they want to leave. Sam tries his hardest to convince them to stay. He even tells them that his father is a climatologist and they will all die in the freezing cold. The people do not listen to Sam and they leave to travel outside. All the people that went outside unfortunately froze to death very soon, just as Sam predicted. Sam’s mother is a doctor working in a hospital with very sick children. She is freezing with the rest of her crew but a rescue teams finds her soon.
Sam and his friends start to burn books to keep warm. They also find food from the vending machines so that they do not starve. Jack, Frank and his friends are still on their way towards New York. At one point they have to walk over very sensitive glass. At one point the glass breaks and Frank falls down, he is barely holding on with his rope. Jason and Jack try to pull him up. Frank notices that their weight will break the glass. He then decides to sacrifice himself to save his friends. Frank snaps the rope and falls to his death.
After some time Laura starts to feel pretty sick. Sam notices this but she does not reveal what is happening with her. They finally talk about their feelings and Sam reveals that he only joined the team because of her. The two of them kiss.
Meanwhile in Mexico Vice President Beckers hears that the President has been caught in the storm and he is probably dead. Becker then officially becomes the new President of the US.
The following morning Sam and Blake realize that Laura has blood poisoning because of the cut on her leg. Sam decides that he must find some sort of cure for her. Soon the group spots an abandoned Russian cargo ship frozen in front of the library. Sam and two other survivors go to find penicillin to save Laura. They arrive at the ship and soon they are attacked by wolves who are on the ship. Sam manages to find the penicillin and they out run the dangerous wolves.
The eye of the storm now fully hits the city and Sam barely manages to get back to safety. The entire building starts to totally freeze. They bring the medicine to Laura but they do not have much time because of the cold. Jason and Jack find shelter in a nearby restaurant as it’s just too cold outside.
Finally after a while they reach the library, everything is buried under massive layers of snow. They find Sam and his friends alive. New York has become totally frozen now. Jack, now reunited with his son, calls for an extraction team. They are flown out of New York to safety. There are thousands of people who have survived the storm in New York so they all have to be rescued. The astronauts are still in space and now they look at the newly formed earth. Most of it is frozen but there is still hope for humanity.