An unprecedented series of violent tornadoes is sweeping across Oklahoma. Tornado chasers, headed by Dr. Jo Harding, attempt to release a groundbreaking device that will allow them to track them and create a more advanced warning system. They are joined by Jo's soon to be ex-husband Bill, a former tornado chaser himself, and his girlfriend Melissa.

After years of increases in the greenhouse effect, havoc is wreaked globally in the form of catastrophic hurricanes, tornadoes, tidal waves, floods and the beginning of a new Ice Age. Paleoclimatologist Jack Hall tries to warn the world while also shepherding to safety his son, trapped in New York after the city is overwhelmed by the start of the new big freeze.

Ray Ferrier is a divorced dockworker and less-than-perfect father. Soon after his ex-wife and her new husband drop off his teenage son and young daughter for a rare weekend visit, a strange and powerful lightning storm touches down.