Astoundingly Long, Intense Phoenix Heat Wave Ends, Meteorologists, Climatologists Agog

Phoenix, Arizona just came out of what was very likely
the most extreme, longest lasting heat wave relative to
average temperatures on record anywhere in the U.S.

The high temperature in Phoenix, Arizona reached 99 degrees on Tuesday, not a record high.

That ended an incredible streak of 21 consecutive days with record high temperatures in that city.  Such a long streak of daily record highs has never been seen before in any weather station with at least a few decades of data. Not even close.  

Meteorologists and climatologists were stunned by the length of this intense hot spell. The just ended hot spell is likely by far the most extreme heat wave relative to average temperatures on record anywhere in the U.S.

A streak like that had been considered impossible. As I noted in an October 5 post about the intense autumn heat wave in the Southwest, the longest consecutive day streak of record highs anywhere in the U.S. had been 14 days in Burlington, Iowa on July 4-17, 1936. Those were the famous old Dust Bowl days.  

The 117 degrees in Phoenix on September 28 was the hottest on record for that month. Setting a September record at the end of the month is even more incredible since you would be expecting the desert heat to be simmering down after Labor Day.

That's especially true since the 117 degree reading broke the old record for the month by nine degrees.  It's very rare for a monthly record to break an old record by more than two degrees. 

Phoenix also set a new record high for October on two days - the 1st and 6th with readings on both days of 113 degrees.  That also shattered the old monthly record by a huge margin of six degrees.

Until this year, it had never reached 110 degrees in Phoenix after September 19.  This year, it was at least 110 degrees on nine days after September 19, the most recent on October 7. 

Relief has come to Phoenix in the form of a pretty aggressive autumn chilly snap. The forecast high on Friday there is only 78 degrees, and showers were actually likely. Saturday looks even cooler, with highs in Phoenix only expected to reach the low to mid 70s.  

Saturday's expected high could threaten a record for the lowest maximum temperature for the date. So that's quite a turnaround. 

Temperatures are expected to rebound into the 90s in Phoenix next week, but at least it won't be in the 100s. again.  Normal highs in Phoenix this time of year are in the upper 80s. 

I'm sure the increase in development, pavement and concrete contributes to the increasing heat in Phoenix. But so does climate change. This heat wave was so far off the charts that observers are saying this would have been impossible without climate change. 

These heat waves are increasingly afflicting Phoenix as they are many other cities globally.  For instance, July, 2023 was the hottest month on record in Phoenix, July, 2024 was merely the second hottest. All of Phoenix's top five hottest Junes, Julys, Augusts and Septembers have occurred since 2003.

Records in Phoenix go back to 1895.