Philly’s summer was so ‘normal’ it was unusual, weather service says
With smoke and thunderstorms, it was one wild summer, so how is that normal?
In a summer when the Southwestern United States and the world set records for heat, the summer of 2023 in Philadelphia was quite exceptional in another respect.
Officially, at least, it was extraordinarily “normal.”
For the June 1-Aug. 31 “meteorological summer” — the average temperature was 75.9 degrees at Philadelphia International Airport, based on preliminary data. That’s just a half degree below the 30-year normal, but the coolest since 2014. The rain total was 12.73 inches; normal is 12.71 inches.
Those numbers are “pretty amazing,” said Dean Iovino, a veteran lead meteorologist at the National Weather Service Office in Mount Holly. “It’s very unusual for it to be that normal.”
Although the astronomical summer doesn’t end until Sept. 23, the world weather community divides the meteorological seasons into tidy three-month increments, mindful that the atmosphere has a certain disdain for calendars. It has been known to snow in April, and to reach 90 in May.
Perhaps as further emphasis of that contempt of predictability, our pumpkin spice-saturated anticipation of fall is about to be interrupted with an unusually timed stretch of 90-degree days.
The official metrics notwithstanding, unofficially, the summer of 2023 was anything but normal around here.
Thunderstorms, including the one that resulted in seven deaths, were reported on 15 days in July, and 10 in August. The average for an entire year is 28 in Philly.
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The weather service’s automated observation doesn’t distinguish between “haze” and “smoke,” and the agency doesn’t keep smoke records, but if it did it would be shocking if this summer didn’t set one. Smoke and/or haze was detected on 18 different days. The region endured a number of “air quality alerts,” and during one of the smoky outbreaks from wildfires in Canada, the Montgomery County emergency center was flooded with 911 calls reporting fire.
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What happened here was inextricably tied to the persistent otherworldly heat in the Southwest, said Dave Dombek, senior meteorologist with AccuWeather. Domes of high pressure baked that region with triple-digit temperatures as the annual monsoonal rains went AWOL.
The average July temperature in Phoenix, 102.7 Fahrenheit, beat the old record by a full 7.2 degrees, according to the Western Regional Climate Center. As so often happens, the East and West are on opposite ends of an atmospheric seesaw.
“The pattern was so locked in,” said Dombek. As heat and dryness persisted out there, a sequence of upper-level storm systems pestered Philadelphia and the Northeast from late June into August.
For Philadelphia, the summer’s journey constituted a strange path to normal, but in reality, “normal” isn’t normal, and probably isn’t what you think.
It is not to be confused with “average,” which is from simple arithmetic. Normal is the result of complicated data analysis.
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About 100 years ago, what is now the World Meteorological Organization decreed that weather agencies compute normals for stations based on 30-year data sets, the logic being that climate is always changing. In recent decades, global warming has accelerated.
The current normals are based on values from Jan. 1, 1991, to Dec. 31, 2020. The data is smoothed to account for day-to-day jumpiness. As the adage attributed to Mark Twain suggests: Climate is what you expect; weather is what you get.
As it turns out, the meteorological fall is about to begin with a Labor Day week heat wave that forecasters say could possibly result in the longest stretch of 90-degree days of the year.
No, that’s not normal.