The climate of Pennsylvania is diverse due to the multitude of

geographic Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and ...

features found within the state. Straddling two major climate zones, the southeastern corner of

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

has the warmest climate. A portion of Greater

Philadelphia Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...

lies at the southernmost tip of the

humid continental climate A humid continental climate is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by four distinct seasons and large seasonal temperature differences, with warm to hot (and often humid) summers and freezing ...

zone, with the city proper being in the

humid subtropical climate A humid subtropical climate is a zone of climate characterized by hot and humid summers, and cool to mild winters. These climates normally lie on the southeast side of all continents (except Antarctica), generally between latitudes 25° and 40° ...

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, and winter

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...

fall amounts are greater. Using the January freezing isotherm, the

(''Cfa'') only exists in parts of Greater Philadelphia and low-lying areas of the lower Susquehanna Valley from

Harrisburg Harrisburg is the capital city of the Pennsylvania, Commonwealth of Pennsylvania, United States, and the county seat of Dauphin County, Pennsylvania, Dauphin County. With a population of 50,135 as of the 2021 census, Harrisburg is the List of c ...

downriver. Pennsylvania's

hardiness zone A hardiness zone is a geographic area defined as having a certain average annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most wide ...

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 Lake Erie ( "eerie") is the fourth largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has t ...

, can receive over of snowfall annually, and the entire state receives an average of of rainfall every year. Floods are more common in March and April than other months of the year.

Tropical cyclones

Tropical cyclones normally threaten the states during the summer and fall, with their main impact being rainfall. Although

Hurricane Agnes Hurricane Agnes in 1972 was the costliest hurricane to hit the United States at the time, causing an estimated $2.1 billion in damage. The hurricane's death toll was 128. The effects of Agnes were widespread, from the Caribbean to Canada, ...

was barely a hurricane at landfall in

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

, its major impact was over the Mid-Atlantic region, where Agnes combined with a non-tropical low to produce widespread rains of to with local amounts up to in western

Schuylkill County Schuylkill County (, ; Pennsylvania Dutch: Schulkill Kaundi) is a county in the Commonwealth of Pennsylvania. It is located in the heart of Pennsylvania's Coal Region and is part of Northeastern Pennsylvania. As of the 2020 census, the populat ...

. These rains produced widespread severe flooding from

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

northward to New York, with other flooding occurring over the western portions of the Carolinas.

has received sustained winds approaching hurricane-force from tropical cyclones in the past.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.

Climate extremes

Temperature

The state record low is , recorded at

Smethport Smethport is a borough and county seat of McKean County, Pennsylvania, United States. The mayor is Wayne V. Foltz. The population was 1,430 at the 2020 census. Smethport is part of the '' Bradford, PA Micropolitan Statistical Area''. Smethport, h ...

on January 5, 1904, while the state record high is , 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 of rain fell in 12 hours near

on July 17, 1942. The NCDC says this is "arguably the greatest 24-hour rainfall on record outside of the tropics".

Precipitation

Tropical cyclones

Climate extremes

Temperature

Precipitation

Rain

Snow

Hurricanes

Climate statistics for selected cities

See also

Notes

References