HARRISBURG — A dangerous heat wave is set to peak Wednesday, with heat index values climbing into the 95 to 100 degree range across southern Pennsylvania and reaching as high as 97 to 101 degrees across southern New Jersey and Delaware, while a separate storm threat targets the northern part of the state the same week.

A ridge of high pressure building across the Ohio Valley and Mid-Atlantic is driving the heat, with dew points climbing toward 70 degrees to add tropical-level humidity on top of the rising temperatures. It has been several weeks since heat index values reached this level in the region.

Where the Heat Hits Hardest

• Southern Pennsylvania: Heat index values of 95 to 100 degrees, among the highest in the region
• Southern New Jersey and Delaware: Heat index readings of 97 to 101 degrees
• Northern Pennsylvania, along and north of I-80: Slightly cooler, in the 87 to 91 degree range, due to storm-related cloud cover
• Peak timing: Heat index values expected to peak Wednesday

The area along and north of I-80 will see a break from the worst of the heat, but not from hazardous weather. Multiple storm clusters are expected to move through that stretch of Pennsylvania between Tuesday and Thursday, and forecasters say the combination of high heat, humidity and elevated wind shear could allow those clusters to produce long-track damaging wind segments.

A Two-Sided Weather Week Taking Shape

Southern Pennsylvania residents should prepare for prolonged heat exposure risks, while those farther north near I-80 face a different hazard entirely as storm season activity ramps up midweek. Anyone spending extended time outdoors in the hotter zones should take precautions given how high the heat index values are trending.

No heat-related illnesses or storm damage have been confirmed yet. This article will be updated as the heat wave and storm threat develop through the week.

Heat Safety Reminders

• Before: Check on elderly neighbors and pets, and plan outdoor activities for early morning or evening
• During peak heat: Stay hydrated, take frequent breaks in air conditioning, and watch for signs of heat exhaustion
• After exposure: Seek shade or cooling immediately if experiencing dizziness, heavy sweating or nausea

For more coverage like this, check back for the latest severe weather updates.