Summers in Phoenix are notoriously hot. But after two punishing summers of record-breaking heat, the latest milestone, set Tuesday, may be the most ominous yet.

At 11 a.m. local time, temperatures in Phoenix hit 100 degrees for the 100th day in a row. The longest previous 100-degree streak was 76 days in 1993. In other words, this year has seen an uninterrupted stretch of 100-degrees days at least 3½ weeks longer than in any other year since records began in 1896.

The relentless heat is testing the will of Phoenix residents. While accustomed to hot summers, many have never endured anything like this. And the heat has proved dangerous for vulnerable groups such as outdoor workers and unhoused populations.

“This is the hottest one I’ve been in,” said Ron Wishon, 55, pushing a bicycle with a flat rear tire through downtown Phoenix.

Wishon has lived in the Valley of the Sun — as the metropolitan area is called — for 45 years, but has never experienced heat like this summer’s.

“I’ve been homeless for 10 years,” Wishon said between gulps of water. “I can’t do another summer out here. No way.”

It was late afternoon on Labor Day and the high temperature was 105 degrees. Wishon was heading toward a 24-hour cooling center at the Phoenix Public Library downtown. The cooling center is part of his daily routine — where he restocks with water. But such cooling facilities don’t allow people to sleep, or stretch out.

“There’s really no place to stay. I walk all night and I try to sleep during the day.”

The cooling center is in an annex building on the north side of the library. Two police cars frame the entrance to a courtyard, where a handful of individuals linger in the welcome shade.

Precious Durant, 66, rests her arms on her walker, which has towels draped down the sides. Her terrier, Buster, lies on his back.

“He likes to lay there because he gets a blast of A/C every time they open that door,” Durant said, motioning toward the main entrance of the cooling center.

This is Durant’s fourth summer in Phoenix. She is waiting for a housing voucher.

“I am really tired. My energy level is so tired,” Durant said, “and I can’t deal with this heat.”

Last year, heat deaths increased 50 percent from 2022, reaching a record of 645 people in Maricopa County, which includes Phoenix. This year, 150 heat deaths have been confirmed by the government and an additional 440 deaths are under investigation.

The streak, which began on May 27 with a high of 102, shows no sign of ending. In fact, the forecast calls for the heat to escalate this week. An excessive-heat warning will be in effect Wednesday through Friday, when highs are expected to approach 110. Long-range forecast models suggest that highs could reach the century mark or more for two more weeks.

The streak remains active after Phoenix experienced its hottest climatological summer (June through August) on record, with an average temperature of 98.9 degrees. Both its average high temperature of 110.4 and average low of 87.5 were also record-setting.

Other notable heat milestones set this summer:

• The hottest June on record (average temperature of 97 degrees), second-hottest July (102.7) and third-hottest August (98.7).

• The most lows at or above 90 degrees, with 37, surpassing last year’s 35.

• Nine calendar-day record highs and 19 record-warm lows during summer. The low of 95 on June 27 was the highest on record for the month.

The scorching summer has pushed 2024’s average temperature to 79.9 degrees, the warmest on record to date and a notch above 79.6 degrees in 2015.

This year’s heat follows a historically hot 2023, which set many of its own heat milestones, including the hottest month on record for a U.S. city, with an average temperature over 100 degrees; a record 31 days in a row with highs at or above 110 degrees; the second-hottest summer on record (behind this year); the city’s all-time warmest low temperature of 97 degrees (on July 19); and a record 16 straight days with lows at or above 90.

Phoenix isn’t the only place in the Southwest experiencing excessive heat this year:

• Palm Springs, Calif. has reached at least 100 degrees on 77 straight days, its fifth-longest streak, trailing 1933’s record streak by 15 days.

• Yuma, Ariz., has reached at least 100 degrees on 96 straight days, its third most, behind 99 days in 1949 and 2006.

Phoenix’s average summer temperature has risen between 8 and 9 degrees since the late 1800s. A rapid increase since the 1960s has culminated in the spike of the last two summers, which is nearly off the charts. The warming in Phoenix is linked to the increasing concentration of greenhouse gases in the atmosphere as well as urbanization.

About 200,000 people lived in Maricopa County in the early 1900s, compared with 4.5 million today. Buildings, roads and other heat-absorbing infrastructure have replaced large undeveloped areas. According to Climate Central, a science communication nonprofit, Phoenix has one of the nation’s largest urban heat island effects, with urban areas at least 8 degrees warmer than their surroundings.

O’Connor reported from Phoenix. Jason Samenow contributed to this report.

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