Ben (Ben Affleck) is a laid-back New York dust jacket copywriter set to marry Bridget (Maura Tierney) in Savannah. At the bachelor party, his 80-year-old grandfather keels over after the stripper makes a few passes at him. Later at the hospital he warns Ben to take his pleasure while he can before the rigor mortis of marriage sets in. This is only the first in a series of potshots at holy matrimony that will reach Ben's ears. When his plane to the South crashes on the runway, Ben is stranded with fellow passenger Sarah (Sandra Bullock), an uninhibited free spirit. They embark on a series of wild and crazy experiences on their way to Savannah using ground transportation.

In this zany romantic comedy directed by Bronwen Hughes (Harriet the Spy), Ben's and his fiancee's resolve to marry each other is tested again and again. While desperately waiting for Ben to show, Bridget discovers that her old boyfriend in Savannah is still madly in love with her. Meanwhile, Sarah plays Zorba the Greek to the cautious and reserved Ben, who doesn't like to reveal his emotions or take risks. They spend time in jail, are pelted by hail, join a caravan of partying potential condominum buyers headed for Florida, and watch the money wired by Ben's parents go up in a fire at the telegraph office.

Sarah turns out to be an eccentric and unexpected spiritual teacher for Ben, revealing the attractions of enthusiasm, joy, and zeal. And he with his good-natured confidence in people points her toward a basic truth about herself. Forces of Nature proclaims that marriage, partnerships, and other relationships are always leaps of faith requiring only a courageous heart and a commitment to the beloved that goes beyond either rhyme or reason.