With nothing more than high clouds and nearly calm winds allowing daytime heating to lift into space overnight, the temperature dropped to 30 at Philadelphia International Airport before dawn Wednesday, the city’s first official freeze of the season.
Readings fell into the mid- and upper 20s outside the airport, and with the air holding about as much moisture as it could handle, it was an ice-scraper situation throughout the region as thick layers of frost developed.
But the seasonal ping-pong is due to return, with highs forecast to crest past 60 Wednesday afternoon, and past 70 on Thursday. “It’s going to be real nice,” said Patrick O’Hara, a meteorologist with the National Weather Service in Mount Holly.
And that’s not going to last either: Another front comes through after sunset Thursday and more December-like temperatures will follow on Marathon weekend in Philadelphia, which is looking dry and generally good for the participants.
The airport was late to the first-freeze party, which is not surprising, given that the official thermometer is located not far from the Delaware River, a swamp, and assorted heat-absorbing paved surfaces and buildings.
Stations in Wilmington, Mount Holly, Blue Bell, and Pottstown all got below freezing almost two weeks ago. From Nov. 4 through Nov. 7, morning lows in Pottstown averaged a full 11 degrees lower than PHL’s, and Wilmington’s, 5 degrees lower.
That the temperature made it all the way down to 30 where the planes take off and land was something of a surprise, said O’Hara, and colder than forecast.
That the first official freeze — defined as the official temperature falling to 32 — held off until Nov. 17 wouldn’t be a surprise: It would be in keeping with recent trends. On average that first freeze has been occurring in mid-November in the 21st century.
That’s several days later than the longer-term average, in keeping with warmer falls associated with climate change. However, that freeze date has exhibited decadal variability, ranging from Oct. 25 in the 1960s to Nov. 16 in the 1930s.