Phoenix’s rash of fall record-breaking temperatures evidence of climate change, expert says

PHOENIX — Phoenix is in the midst of its hottest start to fall in history and an expert believes climate change is a culprit for the abnormal temperatures.

“I think that’s definitely part of the picture here, to have this kind of strong, high pressure system over us is indicative of what we find with climate change,” Randy Cerveny, a professor of geographical sciences at Arizona State University since 1986, told KTAR News 92.3 FM on Thursday. “That’s what we call subtropical high pressure systems, which tend to expand as you warm up the planet and that’s exactly what’s happened this year.”

Phoenix has seen 10 consecutive days of breaking or tying daily heat records as of Thursday, hitting 110 degrees on six of those days. One of those days saw a high temperature of 117 degrees. Until last week, the latest date for a high of at least 110 degrees was Sept. 19.

Cerveny said the consistent record-breaking temperatures are alarming. Typically, Phoenix highs are in the mid-90s for this time of year.

Despite almost a week of high temperatures in the 90s, September 2024 finished as the hottest September on record for Phoenix Sky Harbor Airport by over 2°. A total of 17 (9 high & 8 warm low) temperature records were either broken or tied during the month. #azwx pic.twitter.com/VV73iGl5Fc

— NWS Phoenix (@NWSPhoenix) October 3, 2024

“It’s something that we haven’t seen before … temperatures that are 8 to 15 degrees above normal,” Cerveny said. “Yeah, that’s something that we just haven’t seen before.”

Likely climate change effects to continue in Phoenix

Temperatures will inevitably cool as summer gets further in the rearview mirror, but it’s expected to be a hotter than normal entire fall season.

La Niña is expected during the season, meaning there will likely be a limit for how much moisture comes off the West Coast of Mexico. Higher than normal temperatures are also a staple of the weather pattern.

“Not only are we anticipating that we’re going to have a continuing amount of heat records being set here over the next few weeks, but we’re not going to have rain either, so that combination doesn’t bode well for things like wildfires,” Cerveny said.

Will Phoenix have another abnormally hot summer in 2025?

Looking ahead, Cerveny doesn’t expect next summer to be any less hot than what Phoenix has experienced each of the past two years.

Phoenix just completed its hottest meteorological summer (June-August) ever recorded, averaging 98.9 degrees, shattering the record of 97 degrees from 2023.

“Last year was miserable during the summer. This year was miserable during the summer,” Cerveny said. “When we start to see multiple situations of the same thing happening over and over again, we can start to say ‘yes, there is a trend.’

“I would think that the odds are that next summer is not going to be a fun summer for us again.”

KTAR News 92.3 FM’s Jim Cross contributed to this report.

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