Weather in Central Pennsylvania is growing increasingly unstable today, Tuesday, July 1, 2025, with a high threat of severe thunderstorms capable of unleashing damaging winds, heavy rainfall, and large hail across much of the region. A warm, humid air mass is fueling a volatile atmosphere, especially in areas west of the Bloomsburg–Johnstown line.
Strong storms expected Monday evening across central Pennsylvania
A series of powerful storm systems are forecast to move through central Pennsylvania from Monday afternoon into Tuesday evening. According to the National Weather Service, these multiple rounds of thunderstorms may escalate quickly, with the most dangerous cells likely to develop late this afternoon into tonight. Supercells could form under stronger wind shear, raising the potential for isolated large hail and destructive wind gusts topping 60 mph.
Communities along and west of Interstate 99, including Altoona, State College, and Clearfield, are particularly vulnerable. But even areas eastward, near Harrisburg, Carlisle, and Lancaster, should brace for rapid weather changes this evening and into Tuesday.
Tuesday may bring more organized storm systems
The risk intensifies again Tuesday afternoon, when stronger dynamics aloft could support more structured storm organization. As a cold front pushes east, storms may merge into a linear squall line, increasing the chances for widespread wind damage. Localized flooding may also occur where torrential rain falls repeatedly over the same areas.
Radar trends suggest that parts of South-Central Pennsylvania could experience storm training, which raises concerns for flash flooding, especially near low-lying zones and urban centers like York, Harrisburg, and Chambersburg.
Looking ahead: Summer heat returns by Friday
By midweek, the stormy pattern will shift as high pressure builds in from the west. A return to hot, humid weather is on the horizon, with temperatures climbing toward 90°F (32°C) by Friday in the Harrisburg metro area.
This surge in summer heat will coincide with rising dew points, making for a sweltering July weekend across much of Pennsylvania.
