More than 400 people are suspected to have died from extreme heat in Maricopa county, Arizona so far this summer, according to official figures, as the brutal current heat wave enters its 12th day.
August is on track to be the hottest on record, with temperatures hitting at least 110F (43C) every day apart from one so far. As of 11 August, at least three daily records had been broken including an all-time monthly high of 118F (48C), as well as several nighttime record temperatures, according to Isaac Smith, meteorologist at the National Weather Service (NWS) in Phoenix.
The current extreme heat warning issued by the NWS is the fourth and longest of the summer thus far, and will extend at least through Wednesday night with temperatures forecast to hit 110F (43C). Increased cloud cover and possible thunderstorms will then bring a brief respite towards the weekend but another very hot spell is forecast by the start of next week.
Maricopa county is home to Phoenix, the fifth largest and hottest major US city, as well as several smaller urban hubs dotted amid the Sonora desert including Scottsdale, Tempe and Mesa.
Midway through the hot season, the current official death count – including suspected and confirmed heat-related fatalities – is around 30% lower than this time last year, the second deadliest on record.
In 2025, the county medical examiner’s office has so far confirmed only 35 heat deaths – 17 directly caused by exposure to high temperatures, and 18 cases where heat contributed to the fatality, including by exacerbating chronic medical conditions or the effects of alcohol or methamphetamine. Another 369 suspected heat-related deaths remain under investigation, according to the county’s heat surveillance dashboard which is updated weekly.
June and July were a little cooler than recent years, despite topping 115F (46C) on multiple days, which at least partially explains the lower death toll. Improved access and extended hours at city cooling centres may also be playing a role, according to Dr Nick Staab, the county’s chief medical officer. First responders and hospitals have reportedly gotten better at treating heat stroke and other related temperature related emergencies.
Yet despite the encouraging numbers, Maricopa county is still on track to be the deadliest place for heat in the US after New York City, the country’s largest metropolis, where heat contributes to 525 deaths on average each year.
“With this many cases still under investigation and it only being mid-August, there’s a lot that could still happen,” Staab told KJZZ, the local public radio station.
Heat-related deaths have skyrocketed in Maricopa county over the past decade, with 645 in 2023 compared to 61 in 2014. The county has become increasingly unlivable for many amid record breaking heatwaves driven by the global climate crisis, unchecked urban sprawl and an affordable housing crisis – which combined with patchy mental health and substance misuse services has contributed to a growing unsheltered population.
Last year, heat deaths fell for the first time in a decade to 608, according to official figures, but the city and county have since come under fire for alleged undercounting. A recent investigation by local TV station ABC15 identified multiple cases where heat was discounted as a factor despite the person dying in extreme temperatures.
“People are dying awful, preventable deaths that are not being accounted for in the official figures. We need more consistency and transparency if we’re going to wrap solutions around this public health crisis,” said Stacey Champion, community advocate campaigning for more standardized counting of heat-related deaths in Arizona.
Neither the city nor the county responded immediately to questions surrounding the official death toll.
Heat is the deadliest weather phenomena. But every heat death is preventable, and often indicates a lack of access to adequate shelter, cooling and/or health, addiction and social services.
So far this year, three quarters of heat related deaths have occurred outside, where temperatures in the most built-up, least shadiest parts of Phoenix can be 20 or 30F higher on the sidewalk than the NWS’s airport weather station. Unhoused people account for 40% of deaths, while substance misuse contributed to two thirds.
June was the 11th warmest on record, and July the ninth hottest.
The city, county and state have sought to tackle the increasingly unlivable summer environment through tree canopy initiatives, cooling technologies and an expansion of cooling centres among other policies – in part with the help of Biden-era programs and funds.
But there is little or no hope of ongoing federal support under the Trump administration, which is dismantling environmental justice programs, climate change research and mitigation efforts, as well as access to healthcare, food stamps and other social safety nets. Currently one in four heat deaths in the county occur indoors, and energy costs are predicted to rise significantly under Trump which risks making Maricopa county and beyond even more deadly as summers get hotter.
Meanwhile firefighters are struggling to control at least five major active wildfires across the state, which have so far burnt around 180,000 acres. Hot, dry and windy conditions are fueling the flames in Arizona – as well as fires in California, Utah, Colorado and large swathes of Canada.
