For the 15th consecutive year, the official annual average temperature in Philadelphia — 57.3 degrees Fahrenheit — was higher than the city’s 20th-century annual average.
In the 21st century, the lone exception to the trend was 2003, when the annual temperature, 54.9, finished in a dead heat with that of the 20th-century average.
While warming worldwide hasn’t been uniform, Philadelphia’s temperatures have tracked rather neatly with the overall global trend.
The government’s annual world-temperature report won’t be available for a few weeks; it typically includes data from more than 180 countries, not all of which respond promptly.
» READ MORE: How global average temperatures are measured
But through November, the world was about 1.7 degrees Fahrenheit warmer in 2019 than it was on average in the 20th century, according to the National Centers for Environmental Information, and last year likely will be in the top three warmest.
Since 2000, Philadelphia’s average annual temperature, 56.9, has been a full 2 degrees higher than the 20th-century average. The 2019 average was the 13th warmest among 146 years of record-keeping.
The well-documented trend of warming nights worldwide also was evident in the city’s 2019 numbers. The average daily high, 65.6, was 0.9 degrees above the 30-year climate “normal” value; the average low, 47.2, was 1.7 degrees above the normal.
Those normal values will be recalculated at the end of 2020, noted Jonathan O’Brien, a meteorologist at the National Weather Service Office in Mount Holly. O’Brien said he wouldn’t be surprised to see a degree or two added to what will officially be the new normal.
Extreme times, but not so much for temperatures
In 2019, by the summer solstice, the Mount Holly office had issued more than 136 severe-thunderstorm warnings for the year, compared with 33 the same period of 2018.
That prompted Joe Miketta, the warning-coordinator meteorologist, to declare: “We’re not just making them up. There’s a lot of weather going on. … We’re not trying to scare people."
What might have been the most frightening episode of severe weather around here coincided with Halloween, when a late-night squall line touched up a potent EF-2 tornado in Delaware County and knocked out power to more than 100,000 customers.
But in terms of temperatures, the warmth was consistent but not terribly dramatic, with no long-enduring deadly heat waves or cold spells.
Philadelphia set only one daily high temperature record in 2019, when the high reached 95 on Oct. 2.
Again, in tune with overnight warming, the city did set four records for high daily minimums — 61 on April 13, 71 on May 20, 81 on July 21, and 70 on Oct. 2.
What does all this mean for 2020?
The government’s latest year-ahead outlook has the odds favoring above-normal temperatures in the East, but that’s not to be taken too seriously. The models that have such successes in the short term haven’t exhibited the same skills in the longer ranges.
One of the most important clues they rely upon for the long-lead outlooks is the trend: What’s happened is likely to keep happening.
A trend continues until it doesn’t, and it isn’t always linear, but, yes, for now the temperature trend is unmistakable.