‘Normal’ temperatures reach new highs, and Philly snow totals are also up

With a massive release of data aimed at telling us what is “normal” these days — at least weather-wise — the government on Tuesday affirmed the obvious: Philly and most of the rest of the country have been getting warmer.

Using calculations based on observations from the 1991-to-2020 period, the National Oceanic and Atmospheric Administration decreed that for the next 10 years the normal July high in Philadelphia will be 87.8, 0.7 degrees higher than the previous decade, and the warmest in the available records dating to 1950.

The January high increased a degree, to 41.3, also the highest.

With the exception of the north-central United States, the normal values, which will be in effect until Dec. 31, 2030, are up in most of the nation, according to NOAA’s National Centers for Environmental Information. And the whole country has warmed significantly compared with 20th-century averages, as land-mass warming has outpaced that of the globe generally.

Outside of the Southwest, precipitation amounts have increased — evident in Philly and South Jersey — and so is snowfall in some places, including at Philadelphia International Airport.

“Normal is a tough word for the public to handle,” said David Robinson, the Rutgers University professor who is the New Jersey state climatologist.

» READ MORE: Philly and the East have been setting records, and now has another for rain

It is not your average concept, as in a simple arithmetic mean over a 30-year period. For example, the average high for a May 5 is 70 degrees; the mathematically massaged “normal” is 72, “smoothed to reduce spurious variations in day-to-day increases,” Michael Palecki, physical scientist at NCEI, has explained.

Basing normals on the three most recent decades of weather records represents an attempt to both capture and chase the ever-moving target of climate, which appears to be moving ever-more robustly.

In the view of the World Meteorological Organization, 30 years is considered an adequate sample period and is to be used every 10 years to update the climate “normals.” The United States began doing so in 1950.

Philadelphia has become a wetter place, with the new annual precipitation normal up 6%, from 41.53 inches to 44.11. A similar trend is evident in South Jersey, said Robinson.

Philly’s summers are hotter, and winters milder. In addition to the highs in July and January, overnight minimum temperatures also are higher in both months. The 69.6 in July is a 1.1-degree increase, and January’s 25.6, is a 0.7-degree increase.

Interestingly, seasonal snowfall is up, from 22.4, to 23.1. Given some of the mega-storms in the last decade, “everyone was pretty much expecting that,” said Nicholas Carr, a meteorologist at the National Weather Service Office in Mount Holly.

» READ MORE: What constitutes ‘normal’ weather in Philly and elsewhere is surprisingly complicated, and always changing

New York, Boston, and Detroit also saw increases in snow normals, and that might well be related to general increases in precipitation associated with overall warming; warm air holds more moisture.

The normals aren’t predictive, and as anyone who has spent anytime in the atmosphere knows, day-to-day weather “normal” tends to be abnormal.

NOAA points out for planning purposes that farmers, utilities, the people trying to sell overcoats and swimsuits, degree-day trackers, and other interests need something more than knowing the radical mood changes of weather.

But, no, a 30-year period isn’t magical, said Robinson, the nation’s longest-serving state climatologist.

“It’s a convenient period of time,” he said, “but nothing’s perfect. There’s no convenient way of explaining all this.”