HARRISBURG, PENNSYLVANIA — Well, this is something. Model guidance this morning is showing some genuinely cooler weather heading Pennsylvania’s way, with an early look at afternoon temperatures for Tuesday, September 22, valid 2:00 p.m. EDT, showing many areas stuck in the 50s and low 60s. This will probably be the coldest day across the state since early May, and it arrives right on cue: Tuesday marks the first day of astronomical fall, so Mother Nature is joining right in.
Northwest Pennsylvania Around Erie Sees Some of the Coolest Readings
If you’re in Erie or nearby communities like Fairview, Girard and North East, Tuesday afternoon’s forecast puts you firmly in the upper 50s to around 60 degrees, a sharp departure from the warmth this region has been used to through the summer. Communities just south of Erie, including Meadville and Franklin, are forecast similarly, with readings mostly in the 56 to 60 degree range, making this stretch of northwestern PA one of the coolest corners of the entire state come Tuesday afternoon.
North Central PA From Coudersport to State College Stays Locked in the 50s
Across the state’s north-central region, communities including Coudersport, St. Marys, DuBois, Clearfield and State College are all forecast to stay locked in the 50s through the afternoon, with some spots like Coudersport dipping as low as 54 degrees. If you’re anywhere in this corridor, including Williamsport and Lock Haven to the east, Tuesday is shaping up to be a genuinely chilly, jacket-required afternoon rather than a mild early-fall day.
Northeast PA Including Scranton and Wilkes-Barre Also Stuck in the 50s
Farther east, the Scranton and Wilkes-Barre area falls into the same 50s pattern gripping much of the state’s northern tier, with both cities forecast in the 58 to 59 degree range Tuesday afternoon. Nearby communities including Hazleton, Pottsville and Towanda show similar readings, meaning if you commute or live anywhere across Northeastern Pennsylvania, this is a day to plan for genuinely cool conditions rather than the lingering summer warmth the region has seen recently.
Pittsburgh and Southwestern PA See a Mix of Upper 50s and Low 60s
Out west, Pittsburgh and the surrounding communities, including Greensburg, Washington, Butler and New Castle, are forecast in a slightly milder range than the state’s northern tier, generally in the upper 50s to low 60s. Pittsburgh itself is forecast around 62 degrees, while nearby Washington and Monongahela trend a touch warmer still, into the low 60s, giving residents of Southwestern Pennsylvania a marginally less dramatic cooldown than what’s expected farther north, though still well below what’s typical for late September.
Central PA Around Harrisburg and Altoona Splits Between 50s and Low 60s
Closer to the middle of the state, Altoona, Ebensburg, Johnstown, Somerset and Bedford are all forecast in the mid-50s, some of the coolest readings anywhere in South Central PA. Farther east toward Harrisburg, Lebanon and Chambersburg, temperatures climb slightly into the upper 50s to low 60s, marking the transition zone between the state’s coolest interior valleys and the milder conditions expected closer to the southeastern corner.
Southeastern PA Around Philadelphia Sees the Warmest Readings in the State
If you’re in the Philadelphia area, including Norristown, West Chester, Reading, Lancaster and York, Tuesday’s forecast looks noticeably milder than the rest of the state, with readings generally in the 60s, and some spots near Philadelphia and Chester County even reaching 68 degrees. This corner of the state, including communities along the New Jersey border, is forecast to stay the warmest anywhere in Pennsylvania, offering a smaller taste of the cooldown compared to what’s expected across the northern and central parts of the state.
Why Tuesday Could Be the Coldest Day Since Early May
Forecasters emphasized just how significant this cooldown is by pointing out that Tuesday will probably be the coldest day across the state since early May, a stretch of roughly four and a half months of consistently warmer weather now coming to an end. With daytime temperatures in the 70s and 80s expected to become increasingly scarce as the calendar turns toward October, Tuesday’s chill may be an early preview of the kind of afternoon highs Pennsylvanians should get used to seeing more regularly in the weeks ahead.
Tuesday Marks the First Day of Astronomical Fall
The timing lines up almost perfectly with the calendar: Tuesday, September 22, is the first day of astronomical fall, meaning this cooldown arrives right alongside the official start of the season rather than as an early or late outlier. For residents anywhere across Pennsylvania, from Erie in the northwest to Philadelphia in the southeast, Tuesday offers a genuine, statewide signal that summer’s warmth is giving way to autumn, even if some corners of the state will feel that shift more sharply than others.
