Wilmington is located in the northeast corner of Delaware, on the western bank of the Delaware River where the Christina River joins Brandywine Creek. The city is part of the Atlantic Coastal Plain, which combines flat, low land at sea level with gentle, rolling hills that extend northward into Pennsylvania. The Delaware River forms the city's eastern border with the Atlantic Ocean beyond; Chesapeake Bay lies to the southwest. These large water masses determine the city's climate. Summers are warm and humid, and winters are generally mild. During the summer relative humidity is about 75 percent, and fog is frequent throughout the year. Average annual snowfall is 19.9 inches, but the snow never stays on the ground for more than a few days. Most winter precipitation falls as rain or sleet. Rainfall is heaviest in summer when it comes in the form of thunderstorms. Hurricanes moving northward along the Atlantic Coast occasionally cause heavy rainfall, but winds seldom reach hurricane force in Wilmington. Strong easterly and southeasterly winds sometimes cause high tides in the Delaware River, resulting in flooding of lowlands and damage to riverfront properties.
Area: 10.8 square miles (2000)
Elevation: Approximately 74 feet above sea level
Average Temperatures: January, 32.0° F; July, 76.0° F; annual average, 54.0° F
Average Annual Precipitation: 40.25 inches; 19.9 inches of snow