Climate of Pennsylvania
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.
Precipitation
Western areas of the state, particularly cities near Lake Erie, can receive over Script error: No such module "convert". of snowfall annually, and the entire state receives an average of Script error: No such module "convert". 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.Template:Tropical Cyclone Rainfall in the Mid Atlantic United States 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 Script error: No such module "convert". to Script error: No such module "convert". with local amounts up to Script error: No such module "convert". in western Schuylkill County in Pennsylvania.Template:Tropical Cyclone Point Maxima 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.[3]
Climate extremes
Temperature
The state record low is Script error: No such module "convert"., recorded at Smethport on January 5, 1904, while the state record high is Script error: No such module "convert"., recorded at Phoenixville on July 9 and 10, 1936.
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Precipitation
Rain
| Event[4] | Measurement | Date | Location |
|---|---|---|---|
| Greatest 24-Hour Rainfall | Script error: No such module "convert". | June 22, 1972 (during Hurricane Agnes) |
York |
Note: While the official measured rainfall record is given above, the NCDC notes that an estimated Script error: No such module "convert". 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".[4]
Snow
| Event[4][5] | Measurement | Date | Location |
|---|---|---|---|
| Greatest 24-hour snowfall | Script error: No such module "convert". | March 20, 1958 | Morgantown |
| Greatest two-day snowfall | Script error: No such module "convert". | December 24–26, 2017 | Erie |
| Greatest snow depth | Script error: No such module "convert". | March 22 & 23, 1958 | Gouldsboro |
Hurricanes
| Event[6] | Measurement | Date | Location |
|---|---|---|---|
| Wettest Tropical Cyclone | Script error: No such module "convert". | Agnes (1972) | Western Schuylkill County |
Climate statistics for selected cities
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See also
Notes
References
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- ↑ The Pennsylvania State Climatologist. Annual Average Number of Cloudy Days In Pennsylvania. Script error: No such module "webarchive". Retrieved on 2008-01-28.
- ↑ The Pennsylvania State Climatologist. Climate of Pennsylvania. Script error: No such module "webarchive". Retrieved on 2008-01-28.
- ↑ David M. Roth and Hugh D. Cobb III. RE-ANALYSIS OF THE GALE OF '78 - STORM 9 OF THE 1878 HURRICANE SEASON. Retrieved on 2008-03-05.
- ↑ a b c Script error: No such module "citation/CS1".
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