Philly region’s dry spell intensifies, and the tree pollen is loving it more than allergy sufferers

Pollen commuting on the dry air has been accumulating on car roofs like so much green snow, the wildfire season has been brisk, stream levels are down, and dust is stirring on the nature trails. Overall, it has been mighty dry around Philadelphia the last two months.

No official state drought declarations are imminent in either Pennsylvania or New Jersey, but on Thursday the interagency U.S. Drought Monitor added most of Chester County to its “moderate drought” category and expanded its “abnormally dry” zone, which now covers much of South Jersey and Montgomery and Delaware Counties.

“We welcome a dry spring,” said Andrew Frankenfield, an educator at the Penn State Extension in Montgomery County, noting that it’s good for planting and chores such as hauling manure, “but this is a bit exceptional.”

» READ MORE: A wildfire burned nearly 4,000 acres in South Jersey

Precipitation has been substantially below normal in every county in New Jersey and eastern Pennsylvania during the last 60 days, according to the Middle Atlantic River Forecast Center. Philadelphia’s rainfall has been about half of normal in that period.

Rain is in the forecast for the weekend, and the Climate Prediction Center has the odds favoring above-normal precipitation the rest of the month.

But as they were wont to do with snow during the “winter” of 2022-23, computer models consistently have been overpromising rainfall, said Bill Deger, meteorologist with AccuWeather Inc.

» READ MORE: Computer models were seeing snow in Philly, we weren't

He added the dryness has a way of begetting dryness. “When you dry out the ground, you dry out the water tables,” he said. “There’s less moisture available to go up into the atmosphere and produce the clouds, produce the rain.”

The dry run has extended from northern Virginia through New England, and that’s related to a general pattern of rain-suppressing high pressure, or heavier air, off the East Coast that also has generated warming winds from the south, said Deger.

The opposite has been true out West, which has been on the other end of the upper-air atmospheric seesaw.

» READ MORE: Talk about opposites: What a difference between Philly and the West

Just 1.5% of the western third of the nation is in “extreme” drought or worse, all of it concentrated in central Oregon, according to the Drought Monitor.

The warm winds, the lack of rain, and lack of shade from the trees whose leaves haven’t yet ripened all have contributed to bumping up April temperatures, which through Wednesday were running 6.5 degrees above normal in Philly.

Atmospheric moisture has been wanting, one reason that the National Weather Service has issued four “red flag” wildfire warnings in the last 10 days. In the week that ended April 13, fires charred an estimated 10,000 acres in the Northeast, including nearly 4,000 in a blaze in South Jersey.

And the aridity has been a boon to pollen flight conditions, which couldn’t get much better — or much worse for people allergic to tree pollen, which typically peaks this time of year.

» READ MORE: The tree-pollen season got off to a roaring start, and hasn't quieted

Donald Dvorin, an allergist whose practice is in Mount Laurel and is the region’s certified National Allergy Bureau counter, already has reported “extreme” levels of tree pollen three times since March 21. That would be three more than in 2022′s tree pollen season, when rains were plentiful.

The Asthma Center, in Center City, which began using a machine counting device last year, reported extreme levels several days this month, including on Friday.

Sneezing aside, gardeners could do worse than having a dry spell in April, said Andrew Bunting, vice president of horticulture at the Pennsylvania Horticultural Society. The subsoils are still moist, and it’s not like the ground is baking under July heat.

“The lawns are green,” he said. “Nothing is wilting, per se.”

You’ll want to water grass or anything you just planted, he said, but “you don’t want to overwater things.”

The soil conditions “aren’t terrible,” agreed Frankenfield. “On the flip side, everyone is saying we hope it rains soon.”

The forecasts are calling for drenching showers Saturday night, followed by a significant cooldown with temperatures getting no higher than the 60s through Thursday.

But expect at least one more day of peak pollen conditions with dry air and temperatures heading toward 80 degrees Friday.

As Deger noted, these are strange times: How often does the accumulation of tree pollen outdo all that of the snows of the preceding winter?