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For the third time in five years, Phoenix experienced its hottest summer on record. As had been the case during the prior record-breaking summers of 2020 and 2023, the persistence of the heat, once it set in, was remarkable.

On account of the persistence of the heat, Phoenix saw its longest stretches of 80° or above lows, 100° or above highs, and 105° or above highs: 74 consecutive 80° lows (old record: 51 days), 97 consecutive highs of 100° or above through August 31 (old record: 76 days), and 63 consecutive 105° or above highs (old record: 56 days). Early in September, Phoenix’s streak of 100° days reached and then exceeded 100 consecutive days. Until this year, no major U.S. population center (500,000 or more people) had ever witnessed such a stretch of 100° heat. This year, both East Mesa and Phoenix reached and then exceeded 100 consecutive days.

Anthropogenic climate change amplified by the urban heat island effect is driving a warming of Arizona’s and Phoenix’s summers. Data from a joint May 2024 report published by Climate Central, Red Cross Red Crescent Climate Centre and World Weather Attribution revealed that the influence of climate change has resulted in a 231.1% increase in Arizona’s days with temperatures above the 90th percentile (1991-2020 baseline) over the figure expected without the influence of climate change.

The warming has accelerated in recent decades. Between 1950 and 2023, summers have warmed by 0.6° per decade in Phoenix. Since 1980, summers have warmed by 0.9° per decade.

Select summer data: