Freeze warnings are in effect for Tuesday morning for the entire Philly region
Temperatures could drop to the upper 20s.
In a spring that seems to have exploded rather than sprung, incited by pulses of July-like warmth, April is about to show its crueler side.
The National Weather Service has posted widespread freeze warnings for most of Eastern Pennsylvania and all of New Jersey and Delaware for Tuesday morning.
Temperatures even in parts of the city outside the core of the urban heat island could reach the upper 20s, said Eric Hoeflich, a meteorologist with the weather service in Mount Holly.
He said it would be a close call at the official Philadelphia International Airport measuring site. If it did reach 32 degrees, that would be the latest freeze since 1956, and the fifth latest in records dating to 1873.
But the temperature is not expected to dip to the city’s all-time record the date of 27 degrees, reached in 1875. (No, the thermometer wasn’t at PHL.)
Conditions overnight will be ideal for temperatures to crash, Hoeflich said. Skies are expected to be clear, and winds mostly calm. That would allow any daytime heating to radiate efficiently into space.
Several locations in the region got below freezing Monday morning, including Pottstown and Atlantic City. In Millville, it dropped to 27.
Highs Monday were forecast to top out in the low- and mid-50s, about 10 degrees below seasonal normals, and are expected to be only a few degrees warmer Tuesday afternoon.
Overall, April has been extremely warm, with temperatures averaging more than 8 degrees above normal through Sunday.
However, April is notoriously moody, and historically temperatures have ranged from as low as 14 degrees to as high as 95 as the residue of winter and the ambitious summer continue their jousting, and that has been more than evident this year.
The trees have leafed out in a hurry, and the plant life responded dramatically to last week’s record-setting hot spell that “pushed everything forward quickly,” said Dan Sekowski, associate director of outdoor landscapes at Longwood Gardens.
“So, bloom and leaf-out feel more sudden and concentrated than usual,” he added.
On the grounds of the Winterthur Museum & Gardens, in northern Delaware, the Sargent cherry trees “went form barely budding to full bloom and dropped petals within three or four days,” spokesperson Lisa McVay said Friday, The forsythia bloomed more than two weeks early, she added, and “the Tommy crocuses croaked quickly.
She added, “This weather, and the bloom sequence, is wild,”
It was unclear what effect a freeze might have on plant life, but Longwood’s Sekowski said “anything with tender new growth is vulnerable.” Early perennials, flowering trees, and shrubs that have already broken bud or are in bloom could see some damage, especially to flowers and soft foliage.
“How much impact we see will depend on how low temperatures drop and how long they hold,” he said. “At this point, there’s not much we can do ... beyond standard precautions like covering select sensitive plants where possible.”
It is unlikely that the plants will be threatened by another freeze this season, but the continued dryness may be a growing concern. After prospering from the unusually durable snow cover during the winter, the plants could use a significant natural watering.
While April has been generous with temperature volatility, it has been chary with rainfall. Thus far, just over 1.1 inches of rain has been measured officially, about half of normal, and precipitation has been below normal for seven consecutive months.
The entire region is in a state of “moderate drought,” according to the inter-agency U.S. Drought Monitor, and the drought warning remains in New Jersey, along with wildfire concerns.
Light showers are possible Wednesday and “some signals” in computer guidance are suggesting a wet weekend, Hoeflich said.
Sunday didn’t do much for the increasing precipitation deficits, with a mere 0.01 inches of rain reported at the airport.
Said Hoeflich, “My lawn was looking for a bit more.”
