Philly had its driest May on record, and some parts of the region were even drier

At a time when the foliage was becoming ever more demanding, May rainfall in Burlington County was disturbingly wanting, about 70% shy of normal. What is particularly notable, however, is that last month it was by far the rainiest county in the Philadelphia region.

In fact, the 1.2 inches reported in Burlington in May was double that of runner-up Gloucester County.

With an official 0.24 inches of rain measured at Philadelphia International Airport — 8% of normal — Philly experienced its driest May on record, as did Mount Pocono and Reading, the National Weather Service reported.

» READ MORE: The dryness is a boon to pollen flight

Montgomery and Delaware Counties ended the month with less than 5% of their normal totals, according to the weather service’s Middle Atlantic River Forecast Center, which calculates countywide rain totals based on a sampling of stations.

The dryness has spread like a flash fire, parching “a lot of area pretty rapidly,” said Jason Nolan, a hydrologist with the river center, whose territory extends from central New York to southern Virginia.

Said Richard Heim, a NOAA scientist with the U.S. Drought Monitor, which placed almost all of Pennsylvania in the “abnormally dry” category, “The big thing that caught my eye initially was the extremely low to record low streamflow across almost the entire Northeast.

“Soils are rapidly drying,” he added, noting that the U.S. Department of Agriculture reported this week that 80% of topsoil moisture in Pennsylvania was dry or very dry, up from 32% last week.

The browning of the lawns might well have been further along were it not for the fact that the region got clocked with downpours at the very end of April, said Eric Hoeflich, a meteorologist with the weather service office in Mount Holly. Philadelphia received the equivalent of month’s worth of rain between April 28 and 30.

The timing was especially fortuitous for the region’s farmers and gardeners, who endured quite a peculiar May in which official observations of smoke (one) outnumbered thunderstorms (zero). The Mount Holly office, which is responsible for all of Delaware and much of Eastern Pennsylvania and New Jersey, reported that it issued not a single severe-thunderstorm warning in May.

The office said that had never happened in May in records that date to 1986.

And oddly, the month finished with an average temperature nearly two degrees below normal in Philly. Dryness usually is associated with spring warmth since a lack of moisture allows the sun to spend its energy efficiently heating the ground.

» READ MORE: A snowless winter and the recent dryness may brew a hot summer for Philly

Meteorologists say the coolness and dryness were related to upper-level systems that generated winds from the northwest and also effectively cut off the Mid-Atlantic from an important source of moisture — the Gulf of Mexico.

The results were evident In the Drought Monitor’s report in which 98% of Pennsylvania was considered at least “abnormally dry” — a 12-fold jump from last week. Of that, 5%, including a slice of Chester County, was in “moderate drought.”

The rains were a splash less stingy in New Jersey. None of the Garden State appeared in the dry zones, nor did the northeast half of Philly and slices of Bucks and Montgomery Counties.

“New Jersey hasn’t seen quite the dryness as Pennsylvania,” Heim said.

Philly and some nearby areas did benefit from a coastal storm in mid-May that snubbed areas to the north and west.

» READ MORE: In September, rains came to the rescue. Will it happen again?

For now, neither the Pennsylvania nor New Jersey environmental departments have issued any drought declarations or advisories.

The Philadelphia region has evaded serious drought conditions this century as rain totals generally have increased, a phenomenon likely related to the overall warming of the planet. Warmer air can hold more moisture.

After several drought emergencies starting in 1980, when Pennsylvania began publishing drought maps, the region hasn’t had a single emergency since 2002. It has had any number of impressive dry spells, but the rainy cavalry always has come to the rescue.

In one of the more-emphatic instances, a drought watch was issued for the region on Aug. 5, 2011. By the end of month, a record 19.11 inches of rain had fallen, thanks in large measure to Irene’s remnants.

As to when the region might experience a generous dry-spell-dousing rainfall this time around, “There’s no real soakings on the horizon,” said Hoeflich.

After temperatures make a run into the July-like 90s on Friday, a front is due to approach, and shower chances pop up in the forecasts for Friday night, Saturday, and early in the workweek, but nothing likely to make an impression on the drought map.

“If this continues for a little while longer, we could run into some serious issues,” he added.