Heat advisory for Monday and Tuesday, and likely Wednesday, in Delaware County

The return to average summer temperatures has been pushed back to Thursday in the forecasts, and in the meantime it’ll be highs in the low-to-mid-90s, with a heat advisory in effect from Monday morning to Tuesday night.

The National Weather Service office in Mount Holly, N.J., also adds: “Peak heat indices on Wednesday are forecast to reach or exceed 100 degrees, and therefore an extension of this heat advisory into Wednesday is probable.”

The other weather news for Wednesday is that a cool front is expected to approach the region and set off thunderstorms. The probability of precipitation is listed as less than 50%.

The forecast for Thursday through the weekend is for high temperatures in the 80s in a bit more normalcy for summer, but not much cooling overnights, with the lows staying above 70 degrees around the daybreaks.

But in the more immediate future, on Monday and Tuesday the humidity is expected to be on the increase, which means heat indices will rise and hence, the heat advisory.

On Sunday night at 8, the humidity was 42% at Philadelphia International Airport, the official weather service site in the Philadelphia metro area, a not-uncomfortable reading.

The temperature topped out Sunday at 95 degrees, well off the record for the date. The forecast highs for Monday, Tuesday and Wednesday — 96, 93 and 93, respectively — are all well below date records of 100, 103 and 104, respectively.

The last one is from the scorching summer of 1936 and is tied for the second-highest temperature on record at an official Philadelphia site with July 3, 1966. Both trail 106 degrees on Aug. 5, 1918.