There are many geographic features that help determine the climate and weather events that are seen across Pennsylvania.

Latitude/Longitude: Pennsylvania stretches from 39° 43' N to 42° 16' N, which spans about 298 miles, and from 74° 41' to 80° 31' W or roughly 280 miles wide.
Bodies of Water: Only 2.7% of the area of the state is considered water. Lake Erie borders the Northwestern most part of the state, and major rivers include Alleghany, Delaware, Ohio and Susquehanna Rivers.
Elevation Changes: Elevation changes across the state range from sea level near the Delaware River to the highest point at Mount Davis (3,213 ft.) in Somerset County.
Prevailing Winds: The westerly prevailing winds are found between 30°N and 60°N, and these prevailing winds help steer large scale weather systems and have a large impact on the weather and climate of Pennsylvania. Winds are primarily out of the southwest during the summer and from the northwest during the winter.