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Climate of Pennsylvania
From Wikipedia, the free encyclopedia
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The climate of Pennsylvania is diverse due to the multitude of geographic features found within the state. Straddling two major climate zones, the southeastern corner of Pennsylvania has the warmest climate. A portion of Greater Philadelphia lies at the southernmost tip of the humid continental climate zone, with the city proper being in the humid subtropical climate zone. Still, Philadelphia features colder, snowier winters than most locations with a humid subtropical climate. Moving west toward the mountainous interior of the state, the climate becomes markedly colder, the number of cloudy days increases,[1] and winter snowfall amounts are greater.
Using the January freezing isotherm, the humid subtropical climate (Cfa) only exists in parts of Greater Philadelphia and low-lying areas of the lower Susquehanna Valley from Harrisburg downriver. Pennsylvania's hardiness zone ranges from 5a in high-elevation areas to 7b in parts of Delaware and Philadelphia Counties.
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Precipitation
Western areas of the state, particularly cities near Lake Erie, can receive over 100 inches (254 cm) of snowfall annually, and the entire state receives an average of 41 inches (1,041 mm) of rainfall every year. Floods are more common in March and April than other months of the year. [2]
Tropical cyclones
Tropical cyclones normally threaten the states during the summer and fall, with their main impact being rainfall.[3] Although Hurricane Agnes was barely a hurricane at landfall in Florida, its major impact was over the Mid-Atlantic region, where Agnes combined with a non-tropical low to produce widespread rains of 6 inches (150 mm) to 12 inches (300 mm) with local amounts up to 19 inches (480 mm) in western Schuylkill County in Pennsylvania.[4] These rains produced widespread severe flooding from Virginia northward to New York, with other flooding occurring over the western portions of the Carolinas.
Philadelphia has received sustained winds approaching hurricane-force from tropical cyclones in the past.[5]
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Climate extremes
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Temperature
The state record low is −42 °F (−41 °C), recorded at Smethport on January 5, 1904, while the state record high is 111 °F (44 °C), recorded at Phoenixville on July 9 and 10, 1936.
Precipitation
Rain
Note: While the official measured rainfall record is given above, the NCDC notes that an estimated 34.50 inches (876 mm) of rain fell in 12 hours near Smethport on July 17, 1942. The NCDC says this is "arguably the greatest 24-hour rainfall on record outside of the tropics".[6]
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Hurricanes
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Climate statistics for selected cities
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See also
Notes
- Official records for Allentown were kept at Allentown Gas Company from March 1922 to December 1943, and at Lehigh Valley Int'l since January 1944. For more information, see ThreadEx.
- Official records for Harrisburg kept at downtown from July 1888 to December 1938, Capital City Airport from January 1939 to September 1991, and at Harrisburg Int'l in Middletown since October 1991.[15]
- Official temperature and precipitation measurements for Philadelphia were taken at the Weather Bureau Office in downtown from January 1872 to 19 June 1940, and at Philadelphia Int'l from 20 June 1940 to the present.[19] Snowfall and snow depth records date to 1 January 1884 and 1 October 1948, respectively.[20] In 2006, snowfall measurements were moved to National Park, New Jersey directly across the Delaware River from the airport.[21]
- Records kept September 1874 to June 1935 at the Weather Bureau Office across the Allegheny River from downtown, at Allegheny County Airport from July 1935 to 14 September 1952, and at Pittsburgh Int'l (KPIT) since 15 September 1952. Due to its river valley and urban location as well as elevation, many of the summertime warm minima temperature records set at the WBO have not even come close to being matched at KPIT, which is at-elevation and located in the western suburbs. For more information, see Threadex
- Official records for Avoca/Wilkes-Barre–Scranton kept at downtown Scranton from January 1901 to 17 April 1955 and at Wilkes-Barre/Scranton International Airport since 18 April 1955.[30]
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References
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