Overnight the temperature dropped into the upper 40s in Pottstown, Doylestown, Mount Holly, Trenton, Wrightstown, and at the Northeast Philly airport.
At the official measuring site at International Airport, it got down to 54 around daybreak. That's well shy of any record; temperatures in the 40s have occurred as late as June 23.
That's chilly nonetheless, but a decent warmup is under way. At 11, it already was up to 69 a the airport, which was yesterday's high.
And it's possible that a hot spell due to settle in Sunday could result in the first official heat wave of the season.
The National Weather Service forecast highs Sunday through Tuesday are close to 90, but don't be surprised if they get revised upward a few degrees.
The Commodity Weather Group in Washington says the low 90s are possible, and while the heat is expected to fall short of advisory criteria, the weather service says, "it's certainly something to watch."
Looking ahead, the government's mid-range outlook has the odds tilted to the warm side for the next two weeks.