Updated Aug 1, 2023 - Energy & Environment

Phoenix is first U.S. city with a monthly temperature above 100°F

Data: National Weather Service; Table: Axios Visuals
Data: National Weather Service; Table: Axios Visuals

Phoenix in July became the first major city in the country to reach an average monthly temperature higher than 100°F.

By the numbers: Phoenix's average July temperature of 102.7°F marked its hottest month on record, shattering the previous record of 99.1°F in August 2020.

  • The city saw a record 19 days with overnight minimum temperatures at or above 90°F, an all-time record high minimum temperature of 97°F, and a record-setting 17 days with highs at or above 115°F, according to the National Weather Service forecast office in Phoenix.
  • Phoenix also experienced its longest streak of days with a high temperature 110°F or above, with 31. This beat the old record of 18 straight days.

The intrigue: Usually temperature records are broken by fractions of a degree.

  • The next nine hottest months in the Valley were separated by only 2.3 degrees.
  • Smashing a monthly record by nearly 4°F is unheard of, let alone doing so while establishing another all-time milestone.

Between the lines: Climate scientists say Phoenix's heat record demonstrates the loaded climate dice due to human-caused climate change, with the odds increasingly favoring extreme events.

  • Climate change is also tied to longer, more extreme heat waves globally.
  • A recent study found the Southwest heat wave, which is continuing this week, would have been "virtually impossible" in the absence of human-caused climate change.

Go deeper:

What this summer's weather reveals about climate change

Cruel summer: Climate change on overdrive hits U.S., globe

Record heat "virtually impossible" without climate change

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