Northwestern Pennsylvania

Included Counties: 
Erie, Warren, McKean, Potter, Crawford, Mercer, Venango, Forest, Clarion, Jefferson
Watersheds: 
Ashtabula-Chagrin, Chautauqua-Conneaut, Clarion, Conewango, Connoquenessing, French, Lake Erie, Middle Allegheny-Redbank, Middle Allegheny-Tionesta, Middle West Branch Susquehanna, Pine, Shenango, Sinnemahoning, Tioga, Upper Allegheny, Upper Genesee, Upper West Branch Susquehanna

Geography

Immediately adjacent to Lake Erie is the Lake Erie Plain, a narrow strip of flat, rich land 3 to 4 miles wide. Fine alluvial soils and a favorable climate sustain substantial vegetable and fruit cultivation typical of the area surrounding Lake Erie. The division extends irregularly inland and east, including much of Allegheny National Forest and the cities of Erie, Brookville, and Coudersport.

Overview

Although the northwestern areas of Pennsylvania’s Northwest Climate Division experience a strong lake effect, the climate is primarily continental, characterized by larger temperature ranges than in areas at the same latitude near the Great Lakes which have moderated temperatures. The northwestern sections of the division do, however, reside in the “snowbelt” of northern Pennsylvania and can experience significant lake-effect snow. Because the day-to-day weather is controlled by the movement of pressure systems across the nation, this area seldom experiences prolonged periods of extreme heat or cold, though hot and humid days are more frequent than in more northerly locations. Precipitation is well-distributed throughout the year with slightly more rain falling during the late spring and early summer. Summer precipitation comes mainly in the form of afternoon thunderstorms.

Changes In Precipitation

 in.cm.%
Annual3.89.68.87
Winter0.41.04.65
Spring-0.4-0.9-3.20
Summer1.64.113.19
Fall1.94.717.78

Linear best-fit changes are calculated over the period 1950-2012. Percentage changes are calculated relative to the 1951-1980 historical reference period.

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Changes In Temperature

 °F°C
Annual2.01.1
Winter2.11.2
Spring2.71.5
Summer1.40.8
Fall1.40.8

Linear best-fit changes are calculated over the period 1950-2012. Percentage changes are calculated relative to the 1951-1980 historical reference period.

Seasonal Precipitation

Seasonal Temperature