The effects of Hurricane Isabel in Maryland and Washington, D.C., were among the worst from a tropical cyclone in the Baltimore-Washington Metropolitan Area, United States. Hurricane Isabel formed from a tropical wave on September 6, 2003, in the tropical Atlantic Ocean. It moved northwestward, and within an environment of light wind shear and warm waters, it steadily strengthened to reach peak winds of 165 mph (265 km/h) on September 11. After fluctuating in intensity for four days, Isabel gradually weakened and made landfall on the Outer Banks of North Carolina with winds of 105 mph (165 km/h) on September 18. It quickly weakened over land and became extratropical over western Pennsylvania the next day.
On September 19, Tropical Storm Isabel passed through extreme western Maryland, though its large circulation produced tropical storm force winds throughout the state. About 1.24 million people lost power throughout the state. The worst of its effects came from its storm surge, which inundated areas along the coast and resulted in severe beach erosion. In Eastern Maryland, hundreds of buildings were damaged or destroyed, primarily in Queen Anne's County from tidal flooding. Thousands of houses were affected in Central Maryland, with severe storm surge flooding reported in Baltimore and Annapolis. Washington, D.C., sustained moderate damage, primarily from the winds. Throughout Maryland and Washington, damage totaled about $820 million (2003 USD, $915 million 2006 USD), with only one fatality due to flooding.