Pennsylvania Weather

Pennsylvania climate

Pennsylvania has a humid continental climate with distinct seasonal changes that vary significantly across the state's diverse topography. The southeastern lowlands around Philadelphia experience milder winters and hotter summers than the mountainous interior. The Appalachian Mountains running through the center of the state create orographic effects that enhance precipitation and generate temperature contrasts between the eastern and western slopes.

Lake-effect snow from Lake Erie produces impressive snowfall totals in the northwestern corner of the state, with Erie averaging over 100 inches of snow per season. Severe thunderstorms and occasional tornadoes affect the state during summer, while winter brings nor'easters that can dump heavy snow across the eastern portions. Flooding is a significant hazard, with Tropical Storm Agnes in 1972 causing devastating floods throughout the Susquehanna River valley.

Philadelphia and Pittsburgh, on opposite ends of the state, experience notably different climates. Philadelphia's proximity to the Atlantic gives it slightly warmer winters and a longer growing season, while Pittsburgh's position west of the mountains brings more cloud cover and moderate lake-influenced precipitation. The Pocono Mountains and northern tier receive heavy winter snowfall and provide cooler summer temperatures that attract visitors from the warmer lowlands.