Today's low, though, could be even be even more historic - potentially setting an all-time mark for any day of the year.
Overnight, the lowest temperature was 83 degrees, and the previous highest such mark is 82, last reached on Aug. 8, 2001, the first of the last tandem torchers (or tortures).
It could dip below 82 by midnight, but it should be close, with 83 predicted for 11 p.m., 81 for midnight by the hour-by-hour forecast at weather.com.
Last night, the temperature was 85 at midnight.
So the old mark of 79 for July 7 probably will be toast.
The forecast calls for the overnight low - usually reached hours after midnight - to bottom out at 79 on Thursday.
Temperatures will moderate through the weekend - but less than previous predictions suggested - and afternoon or evening thunderstorms could develop over the next three days.
Thursday will be hot, reaching the mid 90s, and a little more humid, but the excessive heat warning in effect through 8 tonight hasn't been extended into tomorrow, said meteorologist Patrick O'Hara of the National Weather Services' Mount Holly office.
Then highs should hover around the 90 mark through next Tuesday, possibly extending the heat wave - now at four days with highs of at least 90 - to 10 days or more.
"Saturday might be the day to break it, if we get those showers," O'Hara said.
For more on the forecast, go to http://go.philly.com/weather.
Contact staff writer Peter Mucha at 215-854-4342 or email@example.com.