Williamsport lies on the West Branch of the Susquehanna River, hemmed in by the ridges of north-central Pennsylvania. The valley setting gives it a humid continental climate (Köppen Dfa/Dfb border) with warm summers, cold winters, and weather that is tightly bound to the river that runs through town.
Summers are warm and humid, with July highs in the mid 80s and afternoon thunderstorms rolling off the ridges — late August, when the Little League World Series comes to South Williamsport, is typically warm, muggy, and prone to evening storms. Winters are cold, with January lows around 19 °F and roughly 38 inches of snow a year.
Flooding is the signature hazard. The West Branch has a long flood history — the remnants of tropical systems and prolonged spring rain can push the river up quickly, which is why the city sits behind one of the state's major levee systems. Summer thunderstorms and winter ice round out the local concerns.
Climate normals (approximate)
- Warmest month: July — average high around 84 °F
- Coldest month: January — average low around 19 °F
- Annual precipitation: roughly 41 inches
- Annual snowfall: about 38 inches
- Climate type: humid continental (Köppen Dfa/Dfb border)
Common questions
- Does Williamsport flood?
- The West Branch Susquehanna has a long flood history, and the city is protected by a major levee system. The biggest flood threats come from tropical-system remnants and prolonged spring rain.
- What is the weather like for the Little League World Series?
- Late August in South Williamsport is typically warm and humid, with highs in the low-to-mid 80s and a real chance of afternoon or evening thunderstorms interrupting play.
- How much does it snow in Williamsport?
- Roughly 38 inches a year on average, mostly between December and March, with the surrounding ridges often picking up more than the valley floor.
Figures are long-term climate normals (roughly the 1991–2020 reference period) and are meant for context. The live readings at the top of this page always reflect current conditions.