Cold: Surrounded by record lows

One of the most-intense late February cold spells on record reached new heights (or depths) this morning.

In all 40, records were tied or broken in the East on Tuesday, according to the National Weather Service, including a -21 at Concord, N.H., and -19 at Burlington, Vt.

At Mount Pocono, the thermometer got all the way down to 15 below zero Fahrenheit, smashing the record of 14 below set 101 years ago.

Allentown made it to 8 below, beating the old record set in 1948 by a full 12 degrees. The low was 4 below at  Dulles Airport outside Washington.

Closer to Philly, Reading's low of 3 below  was 6 degrees under the old standard set in 1914; below-zero readings could be found in Chester County and South Jersey; and Wilmington tied a record for the date with a low of 6.

At Philadelphia International Airport, however, no records were set as the thermometer bottomed out at 7.

As we've written, the airport is a tough place to get to zero, and if you've flown in or out of Philly recently, we don't have to explain why.

The airport is a heat island unto itself. Although the official thermometer is in a meadow away from the runways, it still isn't immune from the heating affects of all those buildings and paved-over surfaces.

It is near the junction of the Schuylkill and Delaware River and a swamp.

Overnight, however, the main agent keeping the thermometer from going lower was the wind, said Mitchell Gaines at the National Weather Service office in Mount Holly.

Winds were blowing 5 to 7 m.p.h. near daybreak, and were coming from the east and southeast.

Winds inhibit radiational cooling. When the winds are calm, heat stored from the late-February sun is able to radiate into space efficiently, cooling the surface.

Winds stir up the air, causing more mixing and inhibiting that efficient escape.

Not that 7 is a day at the beach, and based on the forecast the weather service is projecting that this month will be the fifth-coldest February in the 141-year period of record with an average temperature of 25.3.

No. 1 on the list would be the 22.2 of 1934, the year of the lowest reading ever in Philly, -11 on Feb. 9; No. 2, 23.0, February 1979; No. 3, 24.5, 1885, and No. 4, 24.6, 1978. Normal for the month is 35.7.

This projects as the second-coldest February in Atlantic City and Allentown, and No. 4 in Wilmington.

Tomorrow temperatures are expected to moderate, going all the way up to 38 in Philadelphia.

That still would be 8 degrees below normal.

We also suspect that the latter half of the month will end up being the very coldest such period on record.