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Phoenix’s recent summers bear the fingerprints of climate change. High temperatures have been increasing. After plunging, the daily temperature range has leveled out, an indication that most of the recent warming is being driven by climate change, not urbanization. Monsoon season has been growing hotter, drier, and more erratic. In the decades ahead, as aridification takes further hold, Phoenix’s rainfall could swing from multi-year droughts to sudden flooding rains.

Friday offered perhaps an early glimpse of that future. The day started warm. The mercury quickly rose to 89°. Shortly after 12 pm, the rumble of thunder boomed across the desert city. The wind picked up dramatically, gusting to 40 mph and then past 50 mph. Then from 1 pm-2 pm, the City was lashed by gusts as high as 56 mph, large hail, and an incredible downpour that sent floodwaters racing through many streets and neighborhoods. During a one-hour period, 1.09” of rain fell. From 2 pm-3 pm, another thunderstorm dumped 0.53” of rain. By the time the day had ended, 1.64” of rain had fallen. That is the seventh highest figure on record for any day in September and the City’s heaviest rainfall since October 13, 2018.

If the historic climate record is representative, Phoenix should see a drier than normal October. The long-term drought should continue.