Dolley Madison, the White House, and the Big Tornado

Many people know the story of Dolley Madison, one of the first First Ladies to live in the White House, and how she saved the famous painting of George Washington as the British attacked and burned Washington, D. C. But few know what happened next. With the U.S. soldiers in retreat and Dolley fleeing, what drove the British soldiers out of the city they were intent on destroying? Was it really a tornado? Or was it something else?