Washington is located in the humid subtropical climate zone (Köppen: Cfa), exhibiting four distinct seasons. Its climate is typical of Mid-Atlantic U.S. areas removed from bodies of water. The District is located in plant hardiness zone 8a near downtown, and zone 7b elsewhere in the city, indicating a temperate climate. Spring and fall are warm, while winter is cool with annual snowfall averaging 14.7 inches (37 cm). Winter temperatures average around 38 °F (3.3 °C) from mid-December to mid-February. Blizzards affect Washington on average once every four to six years. The most violent storms are called "nor'easters", which typically feature high winds, heavy rains, and occasional snow. These storms often affect large sections of the U.S. East Coast.
Summers are hot and humid with a July daily average of 79.2 °F (26.2 °C) and average daily relative humidity around 66%, which can cause medium to moderate personal discomfort. The combination of heat and humidity in the summer brings very frequent thunderstorms, some of which occasionally produce tornadoes in the area. While hurricanes (or their remnants) occasionally track through the area in late summer and early fall, they have often weakened by the time they reach Washington, partly due to the city's inland location. Flooding of the Potomac River, however, caused by a combination of high tide, storm surge, and runoff, has been known to cause extensive property damage in Georgetown.
The highest recorded temperature was 106 °F (41 °C) on July 20, 1930, and August 6, 1918, while the lowest recorded temperature was ?15 °F (?26 °C) on February 11, 1899, during the Great Blizzard of 1899. Over the year, the city averages 37 days hotter than 90 °F (32.2 °C) and 64 nights at or below freezing.
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