90 Million Under Heat Alerts as Phoenix Deaths Double in 110-Degree Heat

Behind the confirmed deaths sat a second, much larger number: 587 more cases still under investigation as of Tuesday, Aug. 18, 2026, according to the Maricopa County Office of the Medical Examiner⁠2. That pending file is what will decide whether 2026 becomes an average bad year, a terrible year, or a record year. CBS News correspondent Jason Allen, cited in national recap reporting, put the under-investigation figure at about 500 in reporting around Aug. 20, a reminder that the queue moves as examiners work through cases⁠4.

The county count did not stand alone. On Aug. 20, 2026, headline reporting put about 90 million individuals across the United States under heat advisories⁠4. That is not a Phoenix story. That is a national map lit up at once, from dry desert heat to humid heat in the Southeast where moisture makes the same temperature far more dangerous to the human body.

What makes the Maricopa County doubling so stark is that it arrived early and kept growing. The 81-versus-35 comparison was reported by Katherine Davis-Young of KJZZ on Aug. 18⁠2. Four days later, by Aug. 22, the county's confirmed toll had already risen to 113, with 584 cases under review, according to KTAR reporter David Iversen⁠3. In other words, the number that led the news on Aug. 20 was out of date within days, and the direction was only upward.

That upward move came as Phoenix itself kept breaking its own daily records. The city hit 115°F and then 117°F on Tuesday and Wednesday, Aug. 25-26, with the 117°F reading tying the record at Sky Harbor Airport⁠5⁠6⁠7. An extreme heat warning ran through Saturday evening, with forecast highs of 114, 113 and 109 degrees and overnight lows around 90⁠5⁠6⁠7. Nights near 90 do not let the body recover, especially for older people, outdoor workers, and anyone without reliable cooling.

The March detail matters because it reframes 2026 as a long season, not a single August spike. KJZZ reported that a record-shattering March heat wave may have led to as many as 28 deaths in the Valley⁠9. Heat mortality in Maricopa County is counted after medical review, not on the day someone collapses, so early-season heat can sit in the files for months before it is confirmed as heat-related⁠2⁠3.

By late August, local reporters were explicitly measuring 2026 against the worst year on record. The Aug. 22 total of 113 confirmed deaths, with 584 still under review, was described as on track to rival the 2023 record of 645 heat deaths⁠3⁠5. That comparison does not mean 2026 had passed 2023. It means the math was suddenly plausible: if even a fraction of the pending cases were confirmed, the year would climb fast.

There is one disagreement in the record worth stating plainly. Local reporting from KJZZ and KTAR consistently gives the August toll as 81 rising to 113 confirmed, with 584 to 587 cases pending⁠2⁠3⁠5. One aggregator, News Usa Today, gives garbled and far lower figures — nearly two dozen confirmed and 282 under investigation — that do not match the county medical examiner figures carried locally⁠8. The sources disagree, and the local medical examiner reporting is treated here as authoritative.

That warning — “'Be vigilant'” — came as KJZZ reported officials urging the public to take continued dangerous heat seriously in late August⁠6. It is spare language, but it fits how heat kills in Phoenix. There is rarely one dramatic moment. There are consecutive days above 110, nights that stay near 90, a warning extended through the weekend, and then more records falling the next week⁠5⁠6⁠7. Vigilance, in that context, means water, shade, check-ins, and cooling, repeated until the pattern breaks.

What the provided sources do not establish is as important as what they do. They do not confirm a specific 110-degree reading in Phoenix on Wednesday, Aug. 19, annual totals for days at or above 110 or nights at or above 90, a trail closure, a hiker's core temperature, round-the-clock cooling centers, multi-day 100-degree streaks in Texas, a first 100-degree day in Miami, or a hot-car death in Texas. Those details appeared in the broadcast caption but have no source in the research file, so they are not part of this account.

The pattern shift that forecasters discussed for the final weekend of August — sub-110-degree highs and rain chances after the Aug. 26 peak — offered the only near-term exit in the sources⁠5⁠6⁠7. Until examiners close the pending files, the full scale of 2026 will remain provisional, but the trajectory is already clear in the county ledger: a March shock, an August doubling, and then records falling again as the toll kept climbing⁠9⁠2⁠3⁠5.