Heat and chill mark September weather in Berks

Keith Mayer, Reading Eagle, Pa.
·5 min read

Oct. 3—Last month was something of a study in temperature extremes in Berks County.

There was the hot first half and the cooler second half, though the chill of the second half did not offset the heat of the first half. And the month ended slightly warmer than normal at 68.5 degrees at Reading Regional Airport, the official National Weather Service site in Berks.

On the precipitation side, rainfall was plentiful. The month officially was above normal but many spots in Berks were well-above normal.

The state Department of Environmental Protection drought monitor still shows Berks in a drought watch, even though the county is above normal overall for the year in a statistic produced by a division of the weather service.

The first half of the month was marked by a six-day heat wave. Six 90-degree days in September are uncommon but not rare. The most 90-degree days in a September is nine in 1961 and 1983.

That month 62 years ago is ranked No. 1 in average temperature for a September in the 125-year Berks database, but the one from 40 years ago isn't found near the top 10 because of so much offsetting cold.

However, six 90-degree days in a row is rare. So rare that the only other September with six in a row is from the first year in the database, 1898. No one began keeping records that year, but it is the earliest year of a continuous database to the present.

The September heat wave set two date records, and the second one, a 98-degree mark on the 7th, was the hottest September day since 1983. It's tied with a 98 on Sept. 1, 2010, for that distinction.

"Corresponding daily low temperatures were not so impressive," said Berks weather historian Jeffrey R. Stoudt, who is also a retired meteorologist. "Three lows of 70 or 71 were well above record-warm-low records for their dates.

"The heat eased after the 9th. But daily mean temperatures did not cool to below normal until the 14th."

Nearly every day until the 29th averaged below normal, though more modestly than the preceding warmth was above normal.

"Thus, September finished at a modest 1.6 degrees above normal," Stoudt added. "Most of the cool was bolstered by a seven-day streak of daily highs in the 60s due to gloomy skies and prevailing northeast winds.

"The cool first day and warm last day of this September bucked the respective trends of warm first half and cool second half."

Stoudt compiled the list of 90-degree days with this story. He is also the founder of the Berks Area Rainfall Networks, which is marking 40 years.

The rainfall

Parts of Berks County collected 8 or more inches of rain, Stoudt added. During the hot half of the month, it was thunderstorms, but the pattern flip brought with it more conventional rainfall.

"The strongest storms delivered up to around 3 inches (of rain) in an hour or two, dropped hail up to ping-pong-ball size, unleashed vivid lightning or generated winds gusting to damaging force. The second rainy stretch came from a slow-moving nor'easter-type low pressure area that was post-tropical remains of Tropical Storm Ophelia, which persisted from the 23rd to nearly month's end."

The rainfall total at the airport was 5.64 inches, just 0.76 above normal.

The normals

However, the normals for temperature and precipitation are generally higher than ever.

Normal is calculated by the weather service as the average of the past three completed decades, in this case 1991 through 2020. Last decade's warmth and heavy precipitation during the final few years have made the normals high.

The 68.5-degree average temperature would have been 3.1 degrees above normal in the 1981 through 2010 dataset. A September only needs a 70-degree average to get on the top 10 list for warmth.

The 5.64-inch monthly rainfall would have been 1.30 above normal with the 1981 through 2010 block.

Berks weather

The particulars

—68.5 degrees: average temperature

—66.9 degrees: Normal

—5.64 inches: rainfall

—4.88 inches: Normal

—90-degree days: 6 (2023 total: 20)

Records

High temperature:

—95 degrees (94: 1898, 1929, 2008)

—98 degrees (93: 1985)

90s in September

Septembers with at least six 90-days/longest streak

—1898: 6/6

—1906: 6/5

—1915: 6/5

—1931: 7/5

—1941: 7/2

—1961: 9/3

—1970: 7/5

—1983: 9/3

—2010: 6/3

—2015: 6/3

—2023: 6/6

Source: National Weather Service/U.S Weather Bureau

Rainfall totals

—Mohnton Hunters Hill, 10.77

—Gouglersville, 10.51

—Mohnton Northridge, 10.30

—Mohnton, 9.96

—Auburn, 9.64

—Cornwall Terrace, 9.42

—Wernersville, 9.26

—Shillington, 9.22

—Bernville, 9.18

—Womelsdorf, 8.91

—Lincoln Park, 8.81

—Knauers, 8.39

—Henningsville, 8.05

—Mohrsville SW, 7.73

—Wyomissing, 7.39

—Shartlesville, 7.32

—Topton, 7.32

—Dryville, 7.24

—New Morgan, 7.05

—Mohrsville, 6.92

—Jacksonwald, 6.91

—Lobachsville, 6.72

—Adamstown, 6.47

—Douglassville, 6.44

—State Hill, 6.25

—West Reading, 6.18

—Reiffton, 6.12

—Boyers Junction, 6.11

—Muhlenberg Park, 6.04

—Hamburg, 5.95

—Mertztown, 5.93

—Elverson NE, 5.92

—Greenfields, 5.80

—Pine Grove, 5.79

—Hopewell, 5.77

—Reading E, 5.59

—Frystown, 5.57

—Boyertown, 5.38

—Amityville, 4.57

—Oley Furnace, 4.50