High above the vast expanse of the Pacific Ocean, a solar eclipse triggers a dramatic drop in the mesosphere's temperature. This sudden cooling causes dense, cold air to penetrate through a weakened ozone layer, leading to the emergence of a menacing ice fog that envelops the region. Among those caught up in this atmospheric upheaval is Jack Tate, a dedicated meteorologist with the International Climate Research Organization (ICRO). Alongside his colleagues Zoe Quinn and Alex, they closely monitor this alarming atmospheric anomaly. However, tragedy strikes when their research vessel is rapidly engulfed by the ice fog, resulting in the deaths of Alex and the rest of the crew on board.
Meanwhile, back in Hobart, Jack faces personal turmoil as he confronts the possible dissolution of his marriage to Emma Tate, a forensic pathologist. Their strained relationship, complicated by his commitment to ICRO over family duties, places a significant strain on Jack's life with their daughter Naomi Tate. After a visit to a divorce lawyer, Jack receives distressing news that their research vessel has run aground, which compels him to investigate further. An autopsy on one of the deceased crew members confirms that they fell victim to a flash freeze roughly three days prior, coinciding with Jack's last communication with Alex. Realizing the urgency of the situation, Zoe manages to salvage essential data from the ill-fated vessel and uncovers satellite images indicating a rapidly expanding cold front.
With time running out, Jack races to rescue Naomi from Ryan's Beach, just as the frigid front claims the lives of her two friends. They narrowly escape the cold wave's grasp and seek refuge within the ICRO research facility. As the icy wave engulfs Hobart, Emma and her parents take shelter in their home, where they hear a child's screams outside. They bravely welcome the girl in, but despite their efforts to provide warmth, she tragically succumbs to cold shock.
The rupture of the ozone layer over Tasmania leads to the creation of additional ozone rifts worldwide, resulting in even more mesospheric cold fronts. The fallout prompts Walter Winslaw, an American researcher at ICRO, to spearhead a collaborative initiative aimed at sealing the rift. The plan involves deploying magnesium phosphate from fighter jets to mitigate the atmospheric crisis. Unfortunately, the aircraft carrier is soon swallowed by a new cold front, rendering the magnesium dispersal ineffective.
Initially doubtful about Jack's instincts, Winslaw ultimately agrees to back a bold new strategy. Jack proposes launching high-altitude rockets packed with ammonium nitrate to explode above the stratosphere. This action would create lightning in the vicinity of the rift, potentially facilitating ozone regeneration. While they work on the payload calculations, Zoe suffers a medical emergency, falling into diabetic ketoacidosis. In a race against time, Jack sets out through the freezing streets of Hobart to retrieve insulin, while Naomi desperately attempts to upload critical simulation data to Walter before the cold front can reach the Vandeburg Space Force Base in California, all while the facility's generators fail.
Upon successfully retrieving the insulin, Jack manages to restart the generator and upload the calculations, enabling the US military to proceed with the missile launch. As the rockets detonate and disperse ammonium nitrate into the stratosphere, a groundbreaking transformation occurs. The ozone layer begins to replenish itself, and as the cold fronts gradually dissipate, a cooperative global effort to disperse more ammonium nitrate helps avert an impending ice age. In the end, Jack and Naomi are reunited with Emma, leading to a heartfelt reconciliation amidst the devastation.
