How hot Philly’s summer got in five charts
Philadelphia hit heat records this summer, due in part to climate change.
It was hard to escape the heat in the summer of 2022: It was hot during the day, hot at night, and hot for long durations.
So The Inquirer took a deep dive into 148 years of data to figure out just how hot it got, and the numbers suggest climate change is having a tangible impact.
August was the hottest it has been in Philadelphia stretching back to 1874, according to an Inquirer analysis of historical weather data. The month ran 4.5 degrees warmer than normal and logged its most 90-degree days ever. Three of the top five hottest summers have come since 2000.
July was no laggard: It tied 1994 for second hottest on record with an average temperature of 82.1. And four of the hottest Julys have come since 2011.
June averaged a slightly-above-normal 74.4 degrees, but it was not particularly hot, and prevented the summer from being the hottest ever.
The summer of 2022 was, however, the second hottest summer ever, with an average temperature of 79.3 degrees. That was just shy of 79.6 degrees reached in 2010.
The data analyzed by The Inquirer focused on the meteorological summer months of June, July, and August, not the astronomical summer that starts with the solstice. “Normal” means the 30-year average temperature, from 1991 to 2020, according to the National Weather Service.
Climate change’s impact
Overall, the trends bear the fingerprints of climate change in Philadelphia, as summers here and throughout the Northeast are growing increasingly warm, scientists say.
» READ MORE: Summer 2022 in Philly is about to set more records
“It’s what we expect to see in a warming climate,” said Jessica Spaccio, a climatologist with the Northeast Regional Climate Center based at Cornell University.
Spaccio said it’s important to differentiate between daily weather patterns and longer-term climate trends. She said many summers see their share of record-setting days or heat waves driven by high pressure systems typical for the time of year. However, climate change adds extra juice, she said, leading to overall hotter summers.
“We have this warming atmosphere that allows us to get hotter than we would have if we didn’t have climate change,” Spaccio said. “So I’m not saying it wouldn’t have been a hot August without climate change, but it would not have been this hot.”
‘An unusually large number’ of 90-degree days
The Northeast Regional Climate Center noted in a blog post that August was similar to July in that it had “an unusually large number of days” with highs at or above 90 and lows at or above 75.
Philadelphia recorded 19 days with highs of at least 90 — a record for August.
Warm nights, warmer ‘normals’
But it’s the hot nights that keep people baking in their beds and bear the hidden fingerprints of climate change.
Consider that Philly recorded 11 days this summer with a low at or above 75, the greatest number ever for August.
And it saw 26 days in total over the summer with a low at or above 75, setting a new record for the summer season — walloping the previous record by five days.
Summers are warmer than 50 years ago
The pattern is notable for how much warmer summers have gotten the past 50 years. All the years with the number of days with lows of 75 degrees or more have come in the past three decades.
Overall, the average summer temperature in Philadelphia has gotten 3.2 degrees warmer since 1970.
And, if you’re thinking relief is on the way with the start of fall: Autumn has also gotten warmer, having risen 2.7 degrees on average since 1970. The National Oceanic and Atmospheric Administration forecasts that September will run warmer than normal.
It also bears noting that normal refers to an average over time. The National Weather Service adjusted the normal last year to reflect the 30-year period of 1991 to 2020. In some cases, the new normal has risen as much as 1 degree from the previous period.
In other words, even normals are warmer than in the past.
This story was clarified to say the new “normal” spans from 1991 to 2020.