An unexplained, local split in the atmosphere causes a series of total unpredictable, yet devastating tornadoes. Rookie fireman Brian Flynn gets trapped in the underground sewage with his girlfriend, deputy mayor James 'Jim' Lawrence and climatologist Dr. Cassie Lawrence's niece Lori. Mayor Leonardo of New York initially refuses to pay proper attention to the phenomenon, a 'reelection threat', so the alert status remains too low for long. Atypical lightning discovered inside tornadoes adds unprecedented dangers. The Lawrences and aeronautics renegade Dr. Lars Liggenhorn conceive a possible solution by launching rockets, but NASA's Dr. Quinn overrules them, imposing standard silver iodine.
