Phoenix Faces Scorching Nights as Heat Records Exceed Daytime Highs

As Phoenix’s summer heat intensifies, the city is setting an unusual pattern — its nighttime temperatures are outpacing daytime highs in breaking records. While only one daytime heat record has been surpassed this summer, an astonishing 10 records for overnight lows have been set since May.

Recently, Phoenix recorded its highest overnight temperature of 97 degrees, matching the previous record set on July 19, 2023. Historically, between 1990 and 2020, the city experienced an average of seven nights annually with lows at or above 90 degrees, based on National Weather Service data. However, the past three years have seen over 20 such nights each year. This year alone, Phoenix has already had 11 nights with temperatures remaining in the 90s, with more expected in the near future.

National Weather Service

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Climate experts attribute the faster warming of nighttime lows compared to daytime highs to human-induced carbon emissions and urban growth, which retain heat even after sunset. Climate Central reports that this phenomenon is not isolated to Phoenix, with summer nights across the U.S. warming by an average of 3 degrees since the 1970s. However, Phoenix stands out with a 6.5-degree increase in nighttime temperatures over the same period.

Climate Central

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Health experts are raising alarms over the public health implications of such extreme overnight heat. In Maricopa County, the number of heat-related fatalities rises when nighttime temperatures remain elevated, preventing residents from cooling down. The Maricopa County Department of Public Health’s medical director, Dr. Nick Staab, emphasized the danger of “sustained heat with high overnight lows” as a significant health risk.