Blazing summertime heat just won’t quit across the desert southwest as a truly historic October heat wave continues this weekend.
Phoenix, Arizona, has seen daytime high temperatures crack the 40-degree mark every day since the last week of September. This is a remarkable event for a region that typically starts seeing relief from the searing heat by the middle of autumn.
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Records fall day after day
Phoenix set a daily record high on Sept. 24 with a high temperature of 42.2°C. The city set another record high of 45.0°C the following day. And yet another the next day. And again the day after that.
The fifth-largest city in the United States, Phoenix’s 1.6 million residents have endured daily record high temperatures for 19 consecutive days as of Saturday, Oct. 12.
Average daytime temperatures here through the first half of October typically come in around 33.1°C. This year, the first half of October is on track to register an average daytime reading of 42-43°C, around ten degrees above seasonal for this time of year.
This remarkable late-season heat wave arrives on the heels of Phoenix measuring its all-time hottest summer on record.
Phoenix’s average temperature this summer was 37.2°C, beating by a full degree the previous hottest summer recorded just last year. The average nighttime low temperature this summer was a balmy 30.8°C—a grim reading that provided little relief from the endless stretch of stifling days.
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Stubborn ridges of high pressure parked over the southwestern United States are responsible for the enduring heat Phoenix has experienced both in recent weeks and over the past few months. This pattern is likely to break soon as a significant upper-level trough swings into western North America next week, finally bringing more seasonable temperatures to the desert southwest.
Extreme heat like we’ve seen in Phoenix in recent years is a hallmark of climate change. A warmer climate sets a higher bar for extreme temperatures, allowing for hotter daytime and nighttime readings compared to past normals.