No bull: Tucson ties its record for hottest summer

Tucson’s withering heat tied for its hottest summer on record, just as summertime temperature records were being broken across Arizona and around the globe.

The average daily temperature here of 90 degrees from June through August also means four of the last five summers — all but 2021 — ranked among Tucson’s hottest five summers since records started being kept here in 1895. The other top five hottest summer here occurred in 1994, the National Weather Service says.

“More misery — that’s for sure,” observed Michael Crimmins, a climate expert, professor and extension specialist for the University of Arizona’s Department of Environmental Science.

This trend is so strong that it’s clear “a climate change signal is definitely driving our summer onslaught,” Crimmins said Friday.

It’s always hard to attribute one event or even a season-long temperature trend to one factor, such as human-caused climate change, said Alex Edwards, a National Weather Service meteorologist in Tucson.

But, “This is the kind of impact we’d expect to see, with the overall trend” of warming temperatures, Edwards said. “It lines up well, especially the warm nights. It’s along the same page for sure, even if it’s just one year.”

Here are some specific summertime temperature figures for Tucson:

• The average high temperature was 103.4 degrees, 3.4 above normal and 1.3 cooler than in 1994, the summer with the hottest average high temperature on record.
• The average low temperature was a record-setting 76.6 degrees, 2.4 higher than normal.
• The average daily temperature of 90 degrees was one-tenth of a degree warmer than that of 1994, which had the warmest summer on record until 2020, and this year broke it. The summer 2024 average temperature finished 2.9 degrees above normal.
• Tucson had 78 days this summer with temperatures of at least 100 degrees — 23 days more than normal. The city experienced 38 days in the summer of at least 105 and six days of at least 110 — both also above the norm.
• Tucson also had a record 67 days where overnight low temperatures didn’t fall below 75, and 21 days in which overnight lows hit at least 80.

This summer’s weather did differ in two important ways from the last record-setting summer of 2020, however.

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That year was constantly derided as having a “nonsoon” season. Only 1.62 inches of rain fell during the entire 2020 season from June 15 through September 30. This year, 5.68 inches of rain has fallen since the start of the monsoon season.

Second, in summer 2020, June temperatures were nowhere near record-breaking, averaging 86.4 degrees. But July and August saw the hottest two months ever recorded by that time in Tucson. This year, all three months had average temperatures of at least 89, and June 2024 finished almost three degrees warmer than June 2020.

This year’s monsoon season started early, in June, and the humidity has been quite high all summer, keeping overnight temperatures up, said Crimmins.

As always, Tucsonans can take some comfort in the fact that Phoenix, at less than half Tucson’s elevation at 1,000 feet, had an even more miserable summer.

Not only did Phoenix’s average summertime temperature of 98.4 break a record, and finish more than eight degrees above Tucson’s summertime average, it has endured 103 straight days of 100-plus temperatures. That’s 28 more than the city’s previous record of 75 straight 100-degree days, set in 1993.

Phoenix’s average high temperature in summer 2024 was 110.4, seven degrees hotter than ours. Its average summertime low was 87.5, more than 10 degrees hotter than in Tucson.

Flagstaff and Yuma’s average summertime temperatures also broke records.

Globally, summer 2024 sweltered to Earth’s hottest on record, making it even more likely than previously thought that this year will end up as the warmest humanity has measured, the Associated Press reported.

Worldwide, the months of June, July and August averaged 62.24 degrees Fahrenheit, according to Copernicus, the European Union’s climate service, AP reported. That’s .05 degrees warmer than the previous record of 2023.

Copernicus records go back to 1940. But American, British and Japanese records, which start in the mid-19th century, show the last decade has been the hottest since regular measurements were taken and likely in about 120,000 years, according to some scientists, AP reported.