On the third consecutive day of an ultra-dry air mass that felt as if it wandered in from Arizona, at least four brushfires were reported in the Philadelphia region and tree and grass pollens evidently had a field day.

The relative humidity at Philadelphia International Airport at 3 p.m. dropped to 13% — matching the 3 p.m. reading at Window Rock, Ariz. — the third straight day in which it had fallen into the teens in Philly.

“It’s certainly unusual,” said Alex Staarmann, a meteorologist with the National Weather Service Office in Mount Holly, “but not unprecedented.”

The weather service doesn’t keep humidity records, but an analysis of available data going back to 1948 shows that levels in the teens were recorded in well fewer than 1% of the hourly reports.

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A “large brushfire” was reported in Kennett Square, Chester County, according to the Breaking News Network. Woods and brush were on fire in Quakertown, Bucks County, which also involved a house and two barns, and a third blaze broke out in Toms River, Ocean County, BNN said. A fourth fire covering up to 20 acres was reported in Chesterfield, Burlington County, late Saturday night.

Further details weren’t available.

The weather service had issued a statement warning of an “elevated risk” of fire on Saturday. However, it stopped short of posting a “red flag warning” for fire danger as it had Thursday and Friday because the winds didn’t meet the criterion, Staarmann said.

Allergy sufferers might have needed some kind of advisory on Saturday. Both tree- and grass-pollen counts were “very high,” according to the Asthma Center, in Center City, which supplies daily counts to The Inquirer.

Air this dry is uncommon around here for the simple reason that the Philadelphia region is in the proximity of a whole lot of water; Arizona has us way beat on sand. But Staarmann said the local aridity is the result of a persistent land breeze from the West and Northwest.

“The flow has been offshore for so long, it’s just a continental air mass,” he said. “There hasn’t been any sea breezes.”

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It does appear that the atmosphere is about to put a damper on the arid spell, and allergy sufferers might be getting some much-welcome relief with the new week.

Thankfully, well after the runners have crossed the finish line at the Blue Cross Broad Street Run on Sunday morning, clouds will build in the afternoon, with an outside chance of showers late in the day, and more likely during the early-morning hours of Monday, Staarmann said.

More showers are possible Tuesday night and Wednesday.

Rain is the mortal enemy of pollen flight.