The US city of 1.6 million residents, the largest in the Sonoran desert, had its hottest-ever summer, breaking the previous 2023 record by nearly two degrees, according to the National Weather Service.
The 113-day streak reached last week smashed Phoenix's previous record of 76 days over 38C set in 1993.
"It's very rare that we see, especially... two record breaking summers like we just experienced," said Matt Salerno, meteorologist at the National Weather Service Phoenix office.
Heat has killed 256 people so far this year in Phoenix's Maricopa County and is the suspected cause of 393 other deaths, according to official data. The county had a record 645 heat deaths last year.
"It is too early to project how totals in 2024 will compare with 2023," said Nailea Leon, a spokesperson for Maricopa County's public health department, adding that year-to-date 2024 heat deaths and suspected deaths were below 2023 levels but the summer was not yet over.
Around half of deaths are of unsheltered people, the county's most vulnerable group.
Deaths peaked in July when Phoenix had regular highs of 47C, a trend climate scientists attribute to global warming from fossil fuel pollution.
Over the last five years, the city has averaged 40 days of 43C or higher compared with about five days at the beginning of the last century, according to the Arizona State Climate Office.
The extreme heat has led to a statewide increase in hectares burned by wildfires in 2024 compared with last year, according to the office's director Erinanne Saffell.
