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A first frost is possible in Philly on Wednesday, with a ‘hard freeze’ outside the city

This would be early: On average, the first frost in Philly doesn't show up until Halloween.

Canada geese waking up on icy Cooper Creek in Cherry Hill in the fall of 2018. A "widespread" frost is expected Thursday morning in the Philly region, with a "hard freeze" possible on the outskirts.
Canada geese waking up on icy Cooper Creek in Cherry Hill in the fall of 2018. A "widespread" frost is expected Thursday morning in the Philly region, with a "hard freeze" possible on the outskirts.Read moreTOM GRALISH / Staff Photographer
    by Anthony R. Wood
    Updated 
    Published 

A “widespread” frost is expected in the Philadelphia region Wednesday morning, and it might even whiten the ground and the rooftops in the city itself.

“It’s going to be close,” said Alex Bodd, meteorologist with the National Weather Service Office in Mount Holly. “It’s going to be creeping down to that 36-degree mark, which usually is about the point we see frost.”

Even Center City — the warmest of all the region’s “heat islands,” where buildings and paved surfaces store daytime solar energy — is included in the weather-service’s frost advisory, although chances are good it will be frost-free, Bodd said.

» READ MORE: The 'heat island' can be an oasis on a chilly morning

The northern and western portions of Bucks, Chester, and Montgomery Counties are under a “freeze warning,” as readings are forecast to drop to near 30 degrees. A hard freeze also is possible in the Pine Barrens, Bodd said, and southeastern Burlington County also under the freeze warning.

Philadelphia’s first frost on average occurs Oct. 31, according to the weather service, although fixing a date is a somewhat elusive exercise.

Frost can occur when temperatures are above freezing, since some surfaces are colder than the air several feet above the ground, where thermometers take their readings. Also, the winds have to be very light or calm.

Conditions Wednesday morning are expected to be ideal. The clear skies and absence of wind will allow daytime heat to escape into space, and air will have enough moisture to freeze on colder surfaces.

» READ MORE: Why this deep South Jersey location is such a thermal outlier

After a chilly Wednesday, with highs in the mid-50s — normal for mid-November — a frosty encore is possible Thursday morning in some areas, said Bodd, although temperatures should be slightly higher.

Readings are expected to remain below normal through the workweek, and the weather Friday night in South Philadelphia should be on the chilly side.

But chances are that the Phillies partisans attending Game 3 of the National League Championship Series will be bringing their own heat to Citizens Bank Park