Washington has a humid subtropical climate (Köppen climate classification: Cfa), typical of Mid-Atlantic U.S. areas removed from bodies of water, with four distinct seasons.

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 mild, with low humidity, while winter brings sustained cool temperatures and annual snowfall averaging 16.6 inches (420 mm). Average winter lows tend to be around 30 °F (-1 °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 tend to be hot and humid, with daily high temperatures in July and August averaging in the high 80s °F (about 30 °C). 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 (−26.1 °C) on February 11, 1899, during the Great Blizzard of 1899. The city averages 36.7 days hotter than 90 °F (32 °C), and 64.4 nights below freezing.

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