By Kate Bilo

PHILADELPHIA (CBS) — After some relief from the sweltering heat of late July, we now head back into an extended heat wave with unusually high humidity. The combination of temperatures in the 90’s and dew points in the 70’s, even upper 70’s, means heat index values will be in the triple digits for the next four days.


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The pattern is being dominated by a large high sitting in the Atlantic, acting as a heat pump to draw in moisture from the south and west. A nearly stationary front near the Great Lakes will not be able to bring any quick relief, and so the region will swelter through the weekend.

An Excessive Heat Warning has been in effect since noon on Thursday and will last through 9 p.m. tonight. The heat index values expected for this afternoon are expected to be 103 to 108.

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People are being asked to call the PCA Heatline at 215-765-9040 to report any heat-related emergencies involving themselves or another person.

In addition to the heat and humidity, we’ll be watching for the possibility of scattered thunderstorms through the weekend. While it doesn’t look like any well-organized systems will impact us until at least Sunday, diurnally-driven storms (those triggered by the heating of the day) will be around each afternoon.

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That aforementioned front finally does try to push through Sunday – but it may get hung up across our region. That means while temperatures may be a bit lower next week, the humidity and threat for storms will remain.