was a factor in the city being ranked as third in the nation for park access and quality in the 2018 ParkScore ranking of the park systems of the nation's 100 most populous cities, according to Trust for Public Land, a non-profit organization. The National Park Service manages most of the of city land owned by the U.S. government. Rock Creek Park is a urban forest in Northwest Washington, which extends through a stream valley that bisects the city. Established in 1890, it is the country's fourth-oldest national park and is home to a variety of plant and animal species, including raccoon, deer, owls, and coyotes. Other National Park Service properties include the Chesapeake and Ohio Canal National Historical Park, the National Mall and Memorial Parks, Theodore Roosevelt Island, Columbia Island, Fort Dupont Park, Meridian Hill Park, Kenilworth Park and Aquatic Gardens, and Anacostia Park. The District of Columbia Department of Parks and Recreation maintains the city's of athletic fields and playgrounds, 40 swimming pools, and 68 recreation centers. The U.S. Department of Agriculture operates the United States National Arboretum in Northeast Washington, D.C.. Climate Washington, D.C. is in the humid subtropical climate zone (Köppen: Cfa). The Trewartha classification is defined as an oceanic climate (Do). Winters are cool to cold with light snow more common but heavy snow not uncommon, and summers are hot and humid. The district is in plant hardiness zone 8a near downtown, and zone 7b elsewhere in the city, indicating a humid subtropical climate. Spring and fall are mild to warm while winter is cool to cold with annual snowfall averaging . Summers are hot and humid with a July daily average of and average daily relative humidity around 66%, which can cause moderate personal discomfort. Heat indices regularly approach at the height of summer. The combination of heat and humidity in the summer brings very frequent thunderstorms, some of which occasionally produce tornadoes in the area. Blizzards affect Washington once every four to six years on average. The most violent storms, known as nor'easters, often impact large regions of the East Coast. From January 27 to 28, 1922, the city officially received of snowfall, the largest snowstorm since official measurements began in 1885. According to notes kept at the time, the city received between from a snowstorm in January 1772. Hurricanes or their remnants occasionally impact the area in late summer and early fall.